Um exoplaneta rochoso do tamanho da Terra, orbita uma estrela pequena e próxima, poderia ser o mundo mais importante já encontrado além do Sistema Solar, disseram os astrônomos.
O planeta localiza-se na constelação de Vela, no hemisfério sul do céu e é próximo o suficiente para que os telescópios possam observar qualquer atmosfera que ele possua, um procedimento que poderia ajudar a registrar algum tipo de vida, se ela existisse em outros planetas, no futuro.
Denominado de GJ 1132b, o exoplaneta é cerca de 16% maior que a Terra, e está localizado a cerca de 39 anos-luz de distância, o que faz com que ele seja três vezes mais próximo da Terra do que qualquer outro exoplaneta rochoso já descoberto. Nessa distância, espera-se que os telescópios sejam capazes de fazer uma análise química de sua atmosfera, a velocidade dos seus ventos e as cores do pôr-do-Sol, que acontecem no exoplaneta.
Os astrônomos registraram o planeta à medida que ele passava na frente da sua estrela, uma estrela do tipo anã vermelha, com somente um quinto do tamanho do Sol. Apesar de muito mais fria e muito mais apagada que o Sol, o GJ 1132b, tem uma órbita tão próxima da estrela que as suas temperaturas superficiais atingem cerca de 260 graus Celsius.
Essa temperatura, obviamente, é muito alta para reter a água em estado líquido na superfície do exoplaneta, fazendo com que ele seja inóspito para a vida, mas não tão quente para queimar toda uma atmosfera que pode ter se formado no planeta.
Final Year Project - Observation and Characterisation of ExoplanetsLucy Stickland
This document summarizes a student report on the observation and characterization of exoplanets. It explores various exoplanet detection techniques, recent increases in Earth-sized planet discoveries, and relationships between stellar and planetary parameters. The student conducted photometry on three known transiting exoplanets - Hat-P-25b, Wasp-43b, and Wasp-2b - using the Sedgwick telescope. Light curves were produced and used to calculate planetary properties. A program called the Exoplanetary Pixelization Transit Model was created and tested to better fit light curves computationally.
The 19 Feb. 2016 Outburst of Comet 67P/CG: An ESA Rosetta Multi-Instrument StudySérgio Sacani
On 19 Feb. 2016 nine Rosetta instruments serendipitously observed an outburst of gas and dust
from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras
and spectrometers ranging from UV over visible to microwave wavelengths, in-situ gas, dust and
plasma instruments, and one dust collector. At 9:40 a dust cloud developed at the edge of an image
in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature
of the outburst that signicantly exceeded the background. The enhancement ranged from 50% of
the neutral gas density at Rosetta to factors >100 of the brightness of the coma near the nucleus.
Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest
enhancements (factors >10). However, even the electron density at Rosetta increased by a factor 3
and consequently the spacecraft potential changed from 16V to 20V during the outburst. A
clear sequence of events was observed at the distance of Rosetta (34 km from the nucleus): within 15
minutes the Star Tracker camera detected fast particles ( 25 ms 1) while 100 m radius particles
were detected by the GIADA dust instrument 1 hour later at a speed of 6 ms 1. The slowest
were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst
originated just outside the FOV of the instruments, the source region and the magnitude of the
outburst could be determined.
VIMS images of the Huygens landing site on Titan acquired during Cassini flybys in October and December 2004 provide insight into surface features near the landing site with spatial resolutions of 14.4-19 km/pixel. Ratio images of the brightest and darkest spectra in the 2.03 μm window reveal a particularly contrasted structure north of the landing site, consistent with local enrichment in exposed water ice. The images also show a possible 150 km diameter impact crater with a central peak. While scattering from haze particles dominates Titan's spectrum, spectral ratios of bright and dark areas suggest differences in surface composition and/or topography related to DISR images of the site.
We describe the discovery of a satellite in orbit about the dwarf planet (136472) Makemake. This
satellite, provisionally designated S/2015 (136472) 1, was detected in imaging data collected with the
Hubble Space Telescope’s Wide Field Camera 3 on UTC April 27, 2015 at 7.80±0.04 magnitudes
fainter than Makemake. It likely evaded detection in previous satellite searches due to a nearly edgeon
orbital configuration, placing it deep within the glare of Makemake during a substantial fraction
of its orbital period. This configuration would place Makemake and its satellite near a mutual event
season. Insufficient orbital motion was detected to make a detailed characterization of its orbital
properties, prohibiting a measurement of the system mass with the discovery data alone. Preliminary
analysis indicates that if the orbit is circular, its orbital period must be longer than 12.4 days, and
must have a semi-major axis &21,000 km. We find that the properties of Makemake’s moon suggest
that the majority of the dark material detected in the system by thermal observations may not reside
on the surface of Makemake, but may instead be attributable to S/2015 (136472) 1 having a uniform
dark surface. This “dark moon hypothesis” can be directly tested with future JWST observations.
We discuss the implications of this discovery for the spin state, figure, and thermal properties of
Makemake and the apparent ubiquity of trans-Neptunian dwarf planet satellites.
The harps n-rocky_planet_search_hd219134b_transiting_rocky_planetSérgio Sacani
Usando o espectrógrafo HARPS-N acoplado ao Telescopio Nazionale Galileo no Observatório de Roque de Los Muchachos, nas Ilhas Canárias, os astrônomos descobriram três exoplanetas, classificados como Super-Terras e um gigante gasoso orbitando uma estrela próxima, chamada de HD 219134.
A HD 219134, também conhecida como HR 8832 é uma estrela do tipo anã-K de quinta magnitude, localizada a aproximadamente 21 anos-luz de distância da Terra, na constelação de Cassiopeia.
A estrela é levemente mais fria e menos massiva que o nosso sol. Ela é tão brilhante que pode ser observada a olho nu.
O sistema planetário HD 219134, abriga um planeta gigante gasoso externo e três planetas internos classificados como super-Terras, um dos quais transita em frente à estrela.
This document summarizes a study of the Corona Australis star-forming region using data from the Herschel space telescope. Key findings include:
1) Herschel maps reveal many cluster members, including some embedded very low-mass objects, several protostars (some extended), and substantial emission from the surrounding cloud.
2) Striking structures are seen, such as bright filaments around the IRS 5 protostar complex and a bubble-shaped rim associated with the Class I object IRS 2.
3) Disks around Class II objects show a wide range of properties, from massive primordial disks to disks with substantial dust depletion or evidence of inside-out evolution. This indicates a diversity of disk evolution
This document summarizes observations of the exoplanet HD 189733b taken with Chandra and XMM-Newton telescopes. The observations detected X-ray emissions from both the planet-hosting star HD 189733A and its companion star HD 189733B. A transit of HD 189733b in front of its star was detected in soft X-rays, with a transit depth of 6-8% compared to 2.41% in the optical. This is interpreted as evidence for an extended atmosphere around the planet that is opaque to X-rays but transparent at optical wavelengths. The magnetic activity of the companion star HD 189733B was also found to be inconsistent with the activity of the planet-hosting star, possibly due to
The nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
Final Year Project - Observation and Characterisation of ExoplanetsLucy Stickland
This document summarizes a student report on the observation and characterization of exoplanets. It explores various exoplanet detection techniques, recent increases in Earth-sized planet discoveries, and relationships between stellar and planetary parameters. The student conducted photometry on three known transiting exoplanets - Hat-P-25b, Wasp-43b, and Wasp-2b - using the Sedgwick telescope. Light curves were produced and used to calculate planetary properties. A program called the Exoplanetary Pixelization Transit Model was created and tested to better fit light curves computationally.
The 19 Feb. 2016 Outburst of Comet 67P/CG: An ESA Rosetta Multi-Instrument StudySérgio Sacani
On 19 Feb. 2016 nine Rosetta instruments serendipitously observed an outburst of gas and dust
from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras
and spectrometers ranging from UV over visible to microwave wavelengths, in-situ gas, dust and
plasma instruments, and one dust collector. At 9:40 a dust cloud developed at the edge of an image
in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature
of the outburst that signicantly exceeded the background. The enhancement ranged from 50% of
the neutral gas density at Rosetta to factors >100 of the brightness of the coma near the nucleus.
Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest
enhancements (factors >10). However, even the electron density at Rosetta increased by a factor 3
and consequently the spacecraft potential changed from 16V to 20V during the outburst. A
clear sequence of events was observed at the distance of Rosetta (34 km from the nucleus): within 15
minutes the Star Tracker camera detected fast particles ( 25 ms 1) while 100 m radius particles
were detected by the GIADA dust instrument 1 hour later at a speed of 6 ms 1. The slowest
were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst
originated just outside the FOV of the instruments, the source region and the magnitude of the
outburst could be determined.
VIMS images of the Huygens landing site on Titan acquired during Cassini flybys in October and December 2004 provide insight into surface features near the landing site with spatial resolutions of 14.4-19 km/pixel. Ratio images of the brightest and darkest spectra in the 2.03 μm window reveal a particularly contrasted structure north of the landing site, consistent with local enrichment in exposed water ice. The images also show a possible 150 km diameter impact crater with a central peak. While scattering from haze particles dominates Titan's spectrum, spectral ratios of bright and dark areas suggest differences in surface composition and/or topography related to DISR images of the site.
We describe the discovery of a satellite in orbit about the dwarf planet (136472) Makemake. This
satellite, provisionally designated S/2015 (136472) 1, was detected in imaging data collected with the
Hubble Space Telescope’s Wide Field Camera 3 on UTC April 27, 2015 at 7.80±0.04 magnitudes
fainter than Makemake. It likely evaded detection in previous satellite searches due to a nearly edgeon
orbital configuration, placing it deep within the glare of Makemake during a substantial fraction
of its orbital period. This configuration would place Makemake and its satellite near a mutual event
season. Insufficient orbital motion was detected to make a detailed characterization of its orbital
properties, prohibiting a measurement of the system mass with the discovery data alone. Preliminary
analysis indicates that if the orbit is circular, its orbital period must be longer than 12.4 days, and
must have a semi-major axis &21,000 km. We find that the properties of Makemake’s moon suggest
that the majority of the dark material detected in the system by thermal observations may not reside
on the surface of Makemake, but may instead be attributable to S/2015 (136472) 1 having a uniform
dark surface. This “dark moon hypothesis” can be directly tested with future JWST observations.
We discuss the implications of this discovery for the spin state, figure, and thermal properties of
Makemake and the apparent ubiquity of trans-Neptunian dwarf planet satellites.
The harps n-rocky_planet_search_hd219134b_transiting_rocky_planetSérgio Sacani
Usando o espectrógrafo HARPS-N acoplado ao Telescopio Nazionale Galileo no Observatório de Roque de Los Muchachos, nas Ilhas Canárias, os astrônomos descobriram três exoplanetas, classificados como Super-Terras e um gigante gasoso orbitando uma estrela próxima, chamada de HD 219134.
A HD 219134, também conhecida como HR 8832 é uma estrela do tipo anã-K de quinta magnitude, localizada a aproximadamente 21 anos-luz de distância da Terra, na constelação de Cassiopeia.
A estrela é levemente mais fria e menos massiva que o nosso sol. Ela é tão brilhante que pode ser observada a olho nu.
O sistema planetário HD 219134, abriga um planeta gigante gasoso externo e três planetas internos classificados como super-Terras, um dos quais transita em frente à estrela.
This document summarizes a study of the Corona Australis star-forming region using data from the Herschel space telescope. Key findings include:
1) Herschel maps reveal many cluster members, including some embedded very low-mass objects, several protostars (some extended), and substantial emission from the surrounding cloud.
2) Striking structures are seen, such as bright filaments around the IRS 5 protostar complex and a bubble-shaped rim associated with the Class I object IRS 2.
3) Disks around Class II objects show a wide range of properties, from massive primordial disks to disks with substantial dust depletion or evidence of inside-out evolution. This indicates a diversity of disk evolution
This document summarizes observations of the exoplanet HD 189733b taken with Chandra and XMM-Newton telescopes. The observations detected X-ray emissions from both the planet-hosting star HD 189733A and its companion star HD 189733B. A transit of HD 189733b in front of its star was detected in soft X-rays, with a transit depth of 6-8% compared to 2.41% in the optical. This is interpreted as evidence for an extended atmosphere around the planet that is opaque to X-rays but transparent at optical wavelengths. The magnetic activity of the companion star HD 189733B was also found to be inconsistent with the activity of the planet-hosting star, possibly due to
The nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
Detection of a_supervoid_aligned_with_the_cold_spot_of_the_cosmic_microwave_b...Sérgio Sacani
This study uses infrared galaxy data from WISE and 2MASS surveys matched with optical data from the Pan-STARRS1 survey to search for a supervoid in the direction of the cosmic microwave background cold spot. Radial galaxy density profiles centered on the cold spot show a large underdensity extending over tens of degrees. Counts in photometric redshift bins within radii of 5 and 15 degrees show significantly low galaxy densities, at 5-6 sigma detection levels. This is consistent with a large 220 Mpc supervoid with an average density contrast of -0.14, centered at a redshift of 0.22. Such a supervoid could plausibly explain the observed cold spot in the cosmic microwave background.
The closest known_flyby_of_a_star_to_the_solar_systemSérgio Sacani
The closest known flyby of a star to the solar system was a low-mass binary star system called WISE J072003.20-084651.2, also known as "Scholz's star". By integrating the orbits of this 0.15 solar mass binary system and the Sun, astronomers found that it passed within 0.25 parsecs (52,000 AU) of the Sun about 70,000 years ago, within the outer bounds of the Oort Cloud. This is the closest encounter with a star to the solar system that has been well-constrained in distance and velocity. While the flyby likely had a negligible impact on long-period comets from the Oort Cloud, it highlights the possibility
A terrestrial planet_candidate_in_a_temperate_orbit_around_proxima_centauriSérgio Sacani
At a distance of 1.295 parsecs,1 the red-dwarf Proxima Centauri (α Centauri C, GL 551,
HIP 70890, or simply Proxima) is the Sun’s closest stellar neighbour and one of the best studied
low-mass stars. It has an effective temperature of only 3050 K, a luminosity of 0.1 per
cent solar, a measured radius of 0.14 R⊙
2 and a mass of about 12 per cent the mass of the
Sun. Although Proxima is considered a moderately active star, its rotation period is 83
days,3 and its quiescent activity levels and X-ray luminosity4 are comparable to the Sun’s. New
observations reveal the presence of a small planet orbiting Proxima with a minimum mass of
1.3 Earth masses and an orbital period of 11.2 days. Its orbital semi-major axis is 0.05 AU,
with an equilibrium temperature in the range where water could be liquid on its surface.5
Jupiter’s interior and deep atmosphere: The initial pole-to-pole passes with ...Sérgio Sacani
On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter,
passing less than 5000 kilometers above the equatorial cloud tops. Images of Jupiter’s
poles show a chaotic scene, unlike Saturn’s poles. Microwave sounding reveals weather
features at pressures deeper than 100 bars, dominated by an ammonia-rich, narrow
low-latitude plume resembling a deeper, wider version of Earth’s Hadley cell. Near-infrared
mapping reveals the relative humidity within prominent downwelling regions. Juno’s
measured gravity field differs substantially from the last available estimate and is one
order of magnitude more precise. This has implications for the distribution of heavy
elements in the interior, including the existence and mass of Jupiter’s core. The observed
magnetic field exhibits smaller spatial variations than expected, indicative of a rich
harmonic content.
A rock composition_for_earth_sized_exoplanetsSérgio Sacani
1) Researchers measured the mass of Kepler-78b, an Earth-sized exoplanet orbiting its host star every 8.5 hours, to be 1.69 ± 0.41 M⊕ using Doppler spectroscopy of the star's radial velocity variations.
2) Given the planet's radius of 1.20 ± 0.09 R⊕, its mean density of 5.3 ± 1.8 g/cm3 is similar to Earth's, suggesting a rocky composition of iron and rock.
3) Kepler-78b is the smallest exoplanet yet characterized with both an accurate mass and radius measurement, extending measurements of planetary composition into the size range of Earth and Venus.
Jupiter’s magnetosphere and aurorae observed by the Juno spacecraft during it...Sérgio Sacani
The Juno spacecraft acquired direct observations of the jovian magnetosphere and auroral
emissions from a vantage point above the poles. Juno’s capture orbit spanned the jovian
magnetosphere from bow shock to the planet, providing magnetic field, charged particle,
and wave phenomena context for Juno’s passage over the poles and traverse of Jupiter’s
hazardous inner radiation belts. Juno’s energetic particle and plasma detectors measured
electrons precipitating in the polar regions, exciting intense aurorae, observed
simultaneously by the ultraviolet and infrared imaging spectrographs. Juno transited
beneath the most intense parts of the radiation belts, passed about 4000 kilometers
above the cloud tops at closest approach, well inside the jovian rings, and recorded the
electrical signatures of high-velocity impacts with small particles as it traversed the equator.
An Earth-mass planet orbiting a Centauri BCarlos Bella
1) Researchers detected an Earth-mass planet orbiting the star Alpha Centauri B.
2) The planet has a minimum mass similar to Earth and orbits its star with a period of 3.236 days, within 0.04 astronomical units.
3) This makes it the lightest planet detected orbiting a Sun-like star and the closest exoplanet to our solar system found to date.
This document summarizes the discovery of an Earth-mass planet orbiting the star Alpha Centauri B. The planet, with a minimum mass similar to Earth, has an orbital period of 3.236 days and is located about 0.04 astronomical units from the star. High-precision radial velocity measurements from the HARPS spectrograph revealed the planet's signal, making it the lightest planet detected around a solar-type star. The discovery demonstrates that current techniques can detect potentially habitable super-Earth planets around Sun-like stars and habitable Earth-like planets around cooler stars.
The transit method detects exoplanets by observing periodic dips in a star's light caused by planets passing in front of the star. This method has discovered over 80% of known exoplanets. It allows determining planet properties like radius, atmosphere composition by analyzing light passing through. The Kepler space telescope extensively uses this method to study exoplanet candidates.
The ExoplanetSat Mission to Detect Transiting Exoplanets with a CShawn Murphy
1) ExoplanetSat is a CubeSat mission that aims to detect Earth-sized exoplanets transiting nearby bright stars using ultra-precise photometry.
2) It will monitor individual target stars to detect the characteristic dip in light level caused by a transiting exoplanet. Any planets detected could then be studied by larger telescopes to characterize their atmospheres.
3) ExoplanetSat's design incorporates a 6cm telescope combined with a fine image stabilization system to achieve near shot-noise limited photometry, allowing detection of Earth-sized planets transiting stars as bright as magnitude 6.
The completeness-corrected rate of stellar encounters with the Sun from the f...Sérgio Sacani
I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial
velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which
come within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the
Oort cloud. 16 stars are found to come within 2 pc (although a few of these have dubious data). This is fewer than were found in a
similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars
with large radial velocity uncertainties (>10 km s−1
), and partly because of missing stars in GDR1 (especially at the bright end). The
closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3 Myr. The Gaia astrometry predict
a much closer passage than pre-Gaia estimates, however: just 16 000 AU (90% confidence interval: 10 000–21 000 AU), which will
bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together
with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function
of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars
with implausibly large velocities), I estimate the rate of stellar encounters within 5 pc averaged over the past and future 5 Myr to be
545±59 Myr−1
. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds
to 87 ± 9 Myr−1 within 2 pc. A more accurate analysis and assessment will be possible with future Gaia data releases.
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
Proper-motion age dating of the progeny of Nova Scorpii ad 1437Sérgio Sacani
‘Cataclysmic variables’ are binary star systems in which one
star of the pair is a white dwarf, and which often generate bright
and energetic stellar outbursts. Classical novae are one type of
outburst: when the white dwarf accretes enough matter from its
companion, the resulting hydrogen-rich atmospheric envelope
can host a runaway thermonuclear reaction that generates a rapid
brightening1–4. Achieving peak luminosities of up to one million
times that of the Sun5
, all classical novae are recurrent, on timescales
of months6
to millennia7
. During the century before and after an
eruption, the ‘novalike’ binary systems that give rise to classical
novae exhibit high rates of mass transfer to their white dwarfs8
.
Another type of outburst is the dwarf nova: these occur in binaries
that have stellar masses and periods indistinguishable from those
of novalikes9
but much lower mass-transfer rates10, when accretiondisk
instabilities11 drop matter onto the white dwarfs. The coexistence
at the same orbital period of novalike binaries and dwarf
novae—which are identical but for their widely varying accretion
rates—has been a longstanding puzzle9
. Here we report the recovery
of the binary star underlying the classical nova eruption of 11 March
ad 1437 (refs 12, 13), and independently confirm its age by propermotion
dating. We show that, almost 500 years after a classical-nova
event, the system exhibited dwarf-nova eruptions. The three other
oldest recovered classical novae14–16 display nova shells, but lack
firm post-eruption ages17,18, and are also dwarf novae at present.
We conclude that many old novae become dwarf novae for part of
the millennia between successive nova eruptions19,
The MESSENGER mission aims to study Mercury through flybys in 2008-2009 and orbital observations beginning in 2011. It launched in 2004 and will use gravity assists at Earth and Venus to reach Mercury's orbit. The spacecraft faces challenges from Mercury's intense solar radiation and requires a large velocity change to achieve orbit. It carries 7 miniaturized instruments to characterize Mercury's composition, geology, magnetic field, exosphere, and magnetosphere. The flybys and orbital phase aim to address outstanding questions about Mercury's formation and evolution.
The mass of_the_mars_sized_exoplanet_kepler_138_b_from_transit_timingSérgio Sacani
Artigo da revista Nature, descreve o trabalho de astrônomos para medir o tamanho e a massa de um exoplaneta parecido com Marte, além de caracterizar por completo o sistema planetário da estrela Kepler-138.
Bright features have been recently discovered by Dawn on Ceres, which extend
previous photometric and Space Telescope observations. These features should produce
distortions of the line profiles of the reflected solar spectrum and therefore an apparent
radial velocity variation modulated by the rotation of the dwarf planet. Here we report
on two sequences of observations of Ceres performed in the nights of 31 July, 26-
27 August 2015 by means of the high-precision HARPS spectrograph at the 3.6-m
La Silla ESO telescope. The observations revealed a quite complex behaviour which
likely combines a radial velocity modulation due to the rotation with an amplitude of
⇡ ±6 m s
This document summarizes the detection of a super-Earth planet orbiting the star GJ 832. Radial velocity data from three telescopes revealed a planet, GJ 832c, with an orbital period of 35.68 days and a minimum mass of 5.4 Earth masses. GJ 832c has a low eccentricity orbit of 0.18 near the inner edge of the star's habitable zone. However, given its large mass, the planet likely has a massive atmosphere that could render it uninhabitable. The GJ 832 system resembles a miniature version of our solar system, with an interior potentially rocky planet and a distant gas giant.
Seven temperate terrestrial planets around the nearby ultracool dwarf star TR...Sérgio Sacani
One aim of modern astronomy is to detect temperate, Earth-like
exoplanets that are well suited for atmospheric characterization.
Recently, three Earth-sized planets were detected that transit (that
is, pass in front of) a star with a mass just eight per cent that of
the Sun, located 12 parsecs away1. The transiting configuration of
these planets, combined with the Jupiter-like size of their host star—
named TRAPPIST-1—makes possible in-depth studies of their
atmospheric properties with present-day and future astronomical
facilities1–3. Here we report the results of a photometric monitoring
campaign of that star from the ground and space. Our observations
reveal that at least seven planets with sizes and masses similar
to those of Earth revolve around TRAPPIST-1. The six inner
planets form a near-resonant chain, such that their orbital periods
(1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small
integers. This architecture suggests that the planets formed farther
from the star and migrated inwards4,5. Moreover, the seven planets
have equilibrium temperatures low enough to make possible the
presence of liquid water on their surfaces6–8.
Four new planets_around_giant_stars_and_the_mass_metallicity_correlation_of_p...Sérgio Sacani
Exoplanet searches have revealed interesting correlations between the stellar properties and the occurrence rate of planets.
In particular, different independent surveys have demonstrated that giant planets are preferentially found around metal-rich stars and
that their fraction increases with the stellar mass.
Aims. During the past six years, we have conducted a radial velocity follow-up program of 166 giant stars, to detect substellar
companions, and characterizing their orbital properties. Using this information, we aim to study the role of the stellar evolution in
the orbital parameters of the companions, and to unveil possible correlations between the stellar properties and the occurrence rate of
giant planets.
Methods. We have taken multi-epoch spectra using FEROS and CHIRON for all of our targets, from which we have computed
precision radial velocities and we have derived atmospheric and physical parameters. Additionally, velocities computed from UCLES
spectra are presented here. By studying the periodic radial velocity signals, we have detected the presence of several substellar
companions.
Results. We present four new planetary systems around the giant stars HIP8541, HIP74890, HIP84056 and HIP95124. Additionally,
we study the correlation between the occurrence rate of giant planets with the stellar mass and metallicity of our targets. We find that
giant planets are more frequent around metal-rich stars, reaching a peak in the detection of f = 16.7+15.5
−5.9 % around stars with [Fe/H] ∼
0.35 dex. Similarly, we observe a positive correlation of the planet occurrence rate with the stellar mass, between M⋆∼ 1.0 - 2.1 M⊙ ,
with a maximum of f = 13.0+10.1
−4.2 %, at M⋆= 2.1 M⊙ .
Conclusions. We conclude that giant planets are preferentially formed around metal-rich stars. Also, we conclude that they are more
efficiently formed around more massive stars, in the stellar mass range of ∼ 1.0 - 2.1 M⊙ . These observational results confirm previous
findings for solar-type and post-MS hosting stars, and provide further support to the core-accretion formation model.
Variability in a_young_lt_transition_planetary_mass_objectSérgio Sacani
Padrões climáticos num misterioso mundo além do nosso Sistema Solar tem sido revelado pela primeira vez, sugere um estudo.
Camadas de nuvens, feitas de poeira quente e gotículas de ferro derretido, foram detectadas num objeto parecido com um planeta descoberto a 75 anos-luz de distância da Terra, dizem os pesquisadores.
As descobertas poderiam melhorar a habilidade dos cientistas de descobrir se condições em planetas distantes seriam capazes de sustentar a vida.
Uma equipe de pesquisadores liderada pela Universidade de Edimburgo, usou um telescópio no Chile para estudar o sistema climático de um mundo distante, conhecido como PSO J318.5-22, que estima-se tenha cerca de 20 milhões de anos de vida.
Os pesquisadores capturaram centenas de imagens infravermelhas do objeto enquanto ele rotacionava em torno do seu próprio eixo num período de 5 horas. Comparando o brilho do PSO J318.5-22, com corpos vizinhos, a equipe descobriu que ele era coberto por múltiplas camadas de nuvens finas e espessas. Essas nuvens causaram as mudanças no brilho do mundo distante enquanto ele executava o seu movimento de rotação, dizem os cientistas.
Astrônomos, usando os dados do Telescópio Espacial de Raios-Gamma Fermi da NASA detectaram pistas de mudanças periódicas no brilho de uma chamada galáxia “ativa”, cujas emissões são alimentadas por um buraco negro gigante. Se confirmada, a descoberta marcaria a primeira emissão cíclica de raios-gamma com anos de duração, já detectada de qualquer galáxia, o que forneceria novas ideias sobre os processos físicos que ocorrem nas proximidades de um buraco negro.
“Observando muitos anos de dados obtidos pelo Large Area Telescope, o LAT, do Fermi, nós identificamos indicações de uma variação com aproximadamente dois anos de comprimento de raios-gamma emitidos pela galáxia conhecida como PG 1553+113”, disse Stefano Ciprini, que coordenou a equipe do Fermi no Centro de Dados Científicos, o ASDC, da Agência Espacial Italiana, em Roma. “Esse sinal é sutil, e dura menos do que 4 ciclos, assim, do mesmo modo que é algo espetacular de se ver é algo que precisa de mais observações”.
Buracos negros supermassivos com uma massa de milhões de vezes a massa do Sol, localizam-se no coração da maioria das galáxias, incluindo a nossa Via Láctea. Em cerca de 1% dessas galáxias, o buraco negro monstruoso, irradia energia equivalente à bilhões de vezes a energia do Sol, emissões que podem variar em escala de tempo de minutos a anos. Os astrônomos se referem a essas como sendo galáxias ativas.
Mais da metade das fontes de raios-gamma observadas pelo LAT do Fermi, são galáxias ativas, chamadas de blazars, como a PG 1553+113. À medida que a matéria cai em direção ao seu buraco negro supermassivo, algumas partículas subatômicas escapam numa velocidade próxima à velocidade da luz em um par de jatos apontados em direções opostas. O que faz um blazar tão brilhante é que um desses jatos de partículas podem estar diretamente apontados para nós.
Detection of a_supervoid_aligned_with_the_cold_spot_of_the_cosmic_microwave_b...Sérgio Sacani
This study uses infrared galaxy data from WISE and 2MASS surveys matched with optical data from the Pan-STARRS1 survey to search for a supervoid in the direction of the cosmic microwave background cold spot. Radial galaxy density profiles centered on the cold spot show a large underdensity extending over tens of degrees. Counts in photometric redshift bins within radii of 5 and 15 degrees show significantly low galaxy densities, at 5-6 sigma detection levels. This is consistent with a large 220 Mpc supervoid with an average density contrast of -0.14, centered at a redshift of 0.22. Such a supervoid could plausibly explain the observed cold spot in the cosmic microwave background.
The closest known_flyby_of_a_star_to_the_solar_systemSérgio Sacani
The closest known flyby of a star to the solar system was a low-mass binary star system called WISE J072003.20-084651.2, also known as "Scholz's star". By integrating the orbits of this 0.15 solar mass binary system and the Sun, astronomers found that it passed within 0.25 parsecs (52,000 AU) of the Sun about 70,000 years ago, within the outer bounds of the Oort Cloud. This is the closest encounter with a star to the solar system that has been well-constrained in distance and velocity. While the flyby likely had a negligible impact on long-period comets from the Oort Cloud, it highlights the possibility
A terrestrial planet_candidate_in_a_temperate_orbit_around_proxima_centauriSérgio Sacani
At a distance of 1.295 parsecs,1 the red-dwarf Proxima Centauri (α Centauri C, GL 551,
HIP 70890, or simply Proxima) is the Sun’s closest stellar neighbour and one of the best studied
low-mass stars. It has an effective temperature of only 3050 K, a luminosity of 0.1 per
cent solar, a measured radius of 0.14 R⊙
2 and a mass of about 12 per cent the mass of the
Sun. Although Proxima is considered a moderately active star, its rotation period is 83
days,3 and its quiescent activity levels and X-ray luminosity4 are comparable to the Sun’s. New
observations reveal the presence of a small planet orbiting Proxima with a minimum mass of
1.3 Earth masses and an orbital period of 11.2 days. Its orbital semi-major axis is 0.05 AU,
with an equilibrium temperature in the range where water could be liquid on its surface.5
Jupiter’s interior and deep atmosphere: The initial pole-to-pole passes with ...Sérgio Sacani
On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter,
passing less than 5000 kilometers above the equatorial cloud tops. Images of Jupiter’s
poles show a chaotic scene, unlike Saturn’s poles. Microwave sounding reveals weather
features at pressures deeper than 100 bars, dominated by an ammonia-rich, narrow
low-latitude plume resembling a deeper, wider version of Earth’s Hadley cell. Near-infrared
mapping reveals the relative humidity within prominent downwelling regions. Juno’s
measured gravity field differs substantially from the last available estimate and is one
order of magnitude more precise. This has implications for the distribution of heavy
elements in the interior, including the existence and mass of Jupiter’s core. The observed
magnetic field exhibits smaller spatial variations than expected, indicative of a rich
harmonic content.
A rock composition_for_earth_sized_exoplanetsSérgio Sacani
1) Researchers measured the mass of Kepler-78b, an Earth-sized exoplanet orbiting its host star every 8.5 hours, to be 1.69 ± 0.41 M⊕ using Doppler spectroscopy of the star's radial velocity variations.
2) Given the planet's radius of 1.20 ± 0.09 R⊕, its mean density of 5.3 ± 1.8 g/cm3 is similar to Earth's, suggesting a rocky composition of iron and rock.
3) Kepler-78b is the smallest exoplanet yet characterized with both an accurate mass and radius measurement, extending measurements of planetary composition into the size range of Earth and Venus.
Jupiter’s magnetosphere and aurorae observed by the Juno spacecraft during it...Sérgio Sacani
The Juno spacecraft acquired direct observations of the jovian magnetosphere and auroral
emissions from a vantage point above the poles. Juno’s capture orbit spanned the jovian
magnetosphere from bow shock to the planet, providing magnetic field, charged particle,
and wave phenomena context for Juno’s passage over the poles and traverse of Jupiter’s
hazardous inner radiation belts. Juno’s energetic particle and plasma detectors measured
electrons precipitating in the polar regions, exciting intense aurorae, observed
simultaneously by the ultraviolet and infrared imaging spectrographs. Juno transited
beneath the most intense parts of the radiation belts, passed about 4000 kilometers
above the cloud tops at closest approach, well inside the jovian rings, and recorded the
electrical signatures of high-velocity impacts with small particles as it traversed the equator.
An Earth-mass planet orbiting a Centauri BCarlos Bella
1) Researchers detected an Earth-mass planet orbiting the star Alpha Centauri B.
2) The planet has a minimum mass similar to Earth and orbits its star with a period of 3.236 days, within 0.04 astronomical units.
3) This makes it the lightest planet detected orbiting a Sun-like star and the closest exoplanet to our solar system found to date.
This document summarizes the discovery of an Earth-mass planet orbiting the star Alpha Centauri B. The planet, with a minimum mass similar to Earth, has an orbital period of 3.236 days and is located about 0.04 astronomical units from the star. High-precision radial velocity measurements from the HARPS spectrograph revealed the planet's signal, making it the lightest planet detected around a solar-type star. The discovery demonstrates that current techniques can detect potentially habitable super-Earth planets around Sun-like stars and habitable Earth-like planets around cooler stars.
The transit method detects exoplanets by observing periodic dips in a star's light caused by planets passing in front of the star. This method has discovered over 80% of known exoplanets. It allows determining planet properties like radius, atmosphere composition by analyzing light passing through. The Kepler space telescope extensively uses this method to study exoplanet candidates.
The ExoplanetSat Mission to Detect Transiting Exoplanets with a CShawn Murphy
1) ExoplanetSat is a CubeSat mission that aims to detect Earth-sized exoplanets transiting nearby bright stars using ultra-precise photometry.
2) It will monitor individual target stars to detect the characteristic dip in light level caused by a transiting exoplanet. Any planets detected could then be studied by larger telescopes to characterize their atmospheres.
3) ExoplanetSat's design incorporates a 6cm telescope combined with a fine image stabilization system to achieve near shot-noise limited photometry, allowing detection of Earth-sized planets transiting stars as bright as magnitude 6.
The completeness-corrected rate of stellar encounters with the Sun from the f...Sérgio Sacani
I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial
velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which
come within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the
Oort cloud. 16 stars are found to come within 2 pc (although a few of these have dubious data). This is fewer than were found in a
similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars
with large radial velocity uncertainties (>10 km s−1
), and partly because of missing stars in GDR1 (especially at the bright end). The
closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3 Myr. The Gaia astrometry predict
a much closer passage than pre-Gaia estimates, however: just 16 000 AU (90% confidence interval: 10 000–21 000 AU), which will
bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together
with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function
of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars
with implausibly large velocities), I estimate the rate of stellar encounters within 5 pc averaged over the past and future 5 Myr to be
545±59 Myr−1
. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds
to 87 ± 9 Myr−1 within 2 pc. A more accurate analysis and assessment will be possible with future Gaia data releases.
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
Proper-motion age dating of the progeny of Nova Scorpii ad 1437Sérgio Sacani
‘Cataclysmic variables’ are binary star systems in which one
star of the pair is a white dwarf, and which often generate bright
and energetic stellar outbursts. Classical novae are one type of
outburst: when the white dwarf accretes enough matter from its
companion, the resulting hydrogen-rich atmospheric envelope
can host a runaway thermonuclear reaction that generates a rapid
brightening1–4. Achieving peak luminosities of up to one million
times that of the Sun5
, all classical novae are recurrent, on timescales
of months6
to millennia7
. During the century before and after an
eruption, the ‘novalike’ binary systems that give rise to classical
novae exhibit high rates of mass transfer to their white dwarfs8
.
Another type of outburst is the dwarf nova: these occur in binaries
that have stellar masses and periods indistinguishable from those
of novalikes9
but much lower mass-transfer rates10, when accretiondisk
instabilities11 drop matter onto the white dwarfs. The coexistence
at the same orbital period of novalike binaries and dwarf
novae—which are identical but for their widely varying accretion
rates—has been a longstanding puzzle9
. Here we report the recovery
of the binary star underlying the classical nova eruption of 11 March
ad 1437 (refs 12, 13), and independently confirm its age by propermotion
dating. We show that, almost 500 years after a classical-nova
event, the system exhibited dwarf-nova eruptions. The three other
oldest recovered classical novae14–16 display nova shells, but lack
firm post-eruption ages17,18, and are also dwarf novae at present.
We conclude that many old novae become dwarf novae for part of
the millennia between successive nova eruptions19,
The MESSENGER mission aims to study Mercury through flybys in 2008-2009 and orbital observations beginning in 2011. It launched in 2004 and will use gravity assists at Earth and Venus to reach Mercury's orbit. The spacecraft faces challenges from Mercury's intense solar radiation and requires a large velocity change to achieve orbit. It carries 7 miniaturized instruments to characterize Mercury's composition, geology, magnetic field, exosphere, and magnetosphere. The flybys and orbital phase aim to address outstanding questions about Mercury's formation and evolution.
The mass of_the_mars_sized_exoplanet_kepler_138_b_from_transit_timingSérgio Sacani
Artigo da revista Nature, descreve o trabalho de astrônomos para medir o tamanho e a massa de um exoplaneta parecido com Marte, além de caracterizar por completo o sistema planetário da estrela Kepler-138.
Bright features have been recently discovered by Dawn on Ceres, which extend
previous photometric and Space Telescope observations. These features should produce
distortions of the line profiles of the reflected solar spectrum and therefore an apparent
radial velocity variation modulated by the rotation of the dwarf planet. Here we report
on two sequences of observations of Ceres performed in the nights of 31 July, 26-
27 August 2015 by means of the high-precision HARPS spectrograph at the 3.6-m
La Silla ESO telescope. The observations revealed a quite complex behaviour which
likely combines a radial velocity modulation due to the rotation with an amplitude of
⇡ ±6 m s
This document summarizes the detection of a super-Earth planet orbiting the star GJ 832. Radial velocity data from three telescopes revealed a planet, GJ 832c, with an orbital period of 35.68 days and a minimum mass of 5.4 Earth masses. GJ 832c has a low eccentricity orbit of 0.18 near the inner edge of the star's habitable zone. However, given its large mass, the planet likely has a massive atmosphere that could render it uninhabitable. The GJ 832 system resembles a miniature version of our solar system, with an interior potentially rocky planet and a distant gas giant.
Seven temperate terrestrial planets around the nearby ultracool dwarf star TR...Sérgio Sacani
One aim of modern astronomy is to detect temperate, Earth-like
exoplanets that are well suited for atmospheric characterization.
Recently, three Earth-sized planets were detected that transit (that
is, pass in front of) a star with a mass just eight per cent that of
the Sun, located 12 parsecs away1. The transiting configuration of
these planets, combined with the Jupiter-like size of their host star—
named TRAPPIST-1—makes possible in-depth studies of their
atmospheric properties with present-day and future astronomical
facilities1–3. Here we report the results of a photometric monitoring
campaign of that star from the ground and space. Our observations
reveal that at least seven planets with sizes and masses similar
to those of Earth revolve around TRAPPIST-1. The six inner
planets form a near-resonant chain, such that their orbital periods
(1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small
integers. This architecture suggests that the planets formed farther
from the star and migrated inwards4,5. Moreover, the seven planets
have equilibrium temperatures low enough to make possible the
presence of liquid water on their surfaces6–8.
Four new planets_around_giant_stars_and_the_mass_metallicity_correlation_of_p...Sérgio Sacani
Exoplanet searches have revealed interesting correlations between the stellar properties and the occurrence rate of planets.
In particular, different independent surveys have demonstrated that giant planets are preferentially found around metal-rich stars and
that their fraction increases with the stellar mass.
Aims. During the past six years, we have conducted a radial velocity follow-up program of 166 giant stars, to detect substellar
companions, and characterizing their orbital properties. Using this information, we aim to study the role of the stellar evolution in
the orbital parameters of the companions, and to unveil possible correlations between the stellar properties and the occurrence rate of
giant planets.
Methods. We have taken multi-epoch spectra using FEROS and CHIRON for all of our targets, from which we have computed
precision radial velocities and we have derived atmospheric and physical parameters. Additionally, velocities computed from UCLES
spectra are presented here. By studying the periodic radial velocity signals, we have detected the presence of several substellar
companions.
Results. We present four new planetary systems around the giant stars HIP8541, HIP74890, HIP84056 and HIP95124. Additionally,
we study the correlation between the occurrence rate of giant planets with the stellar mass and metallicity of our targets. We find that
giant planets are more frequent around metal-rich stars, reaching a peak in the detection of f = 16.7+15.5
−5.9 % around stars with [Fe/H] ∼
0.35 dex. Similarly, we observe a positive correlation of the planet occurrence rate with the stellar mass, between M⋆∼ 1.0 - 2.1 M⊙ ,
with a maximum of f = 13.0+10.1
−4.2 %, at M⋆= 2.1 M⊙ .
Conclusions. We conclude that giant planets are preferentially formed around metal-rich stars. Also, we conclude that they are more
efficiently formed around more massive stars, in the stellar mass range of ∼ 1.0 - 2.1 M⊙ . These observational results confirm previous
findings for solar-type and post-MS hosting stars, and provide further support to the core-accretion formation model.
Variability in a_young_lt_transition_planetary_mass_objectSérgio Sacani
Padrões climáticos num misterioso mundo além do nosso Sistema Solar tem sido revelado pela primeira vez, sugere um estudo.
Camadas de nuvens, feitas de poeira quente e gotículas de ferro derretido, foram detectadas num objeto parecido com um planeta descoberto a 75 anos-luz de distância da Terra, dizem os pesquisadores.
As descobertas poderiam melhorar a habilidade dos cientistas de descobrir se condições em planetas distantes seriam capazes de sustentar a vida.
Uma equipe de pesquisadores liderada pela Universidade de Edimburgo, usou um telescópio no Chile para estudar o sistema climático de um mundo distante, conhecido como PSO J318.5-22, que estima-se tenha cerca de 20 milhões de anos de vida.
Os pesquisadores capturaram centenas de imagens infravermelhas do objeto enquanto ele rotacionava em torno do seu próprio eixo num período de 5 horas. Comparando o brilho do PSO J318.5-22, com corpos vizinhos, a equipe descobriu que ele era coberto por múltiplas camadas de nuvens finas e espessas. Essas nuvens causaram as mudanças no brilho do mundo distante enquanto ele executava o seu movimento de rotação, dizem os cientistas.
Astrônomos, usando os dados do Telescópio Espacial de Raios-Gamma Fermi da NASA detectaram pistas de mudanças periódicas no brilho de uma chamada galáxia “ativa”, cujas emissões são alimentadas por um buraco negro gigante. Se confirmada, a descoberta marcaria a primeira emissão cíclica de raios-gamma com anos de duração, já detectada de qualquer galáxia, o que forneceria novas ideias sobre os processos físicos que ocorrem nas proximidades de um buraco negro.
“Observando muitos anos de dados obtidos pelo Large Area Telescope, o LAT, do Fermi, nós identificamos indicações de uma variação com aproximadamente dois anos de comprimento de raios-gamma emitidos pela galáxia conhecida como PG 1553+113”, disse Stefano Ciprini, que coordenou a equipe do Fermi no Centro de Dados Científicos, o ASDC, da Agência Espacial Italiana, em Roma. “Esse sinal é sutil, e dura menos do que 4 ciclos, assim, do mesmo modo que é algo espetacular de se ver é algo que precisa de mais observações”.
Buracos negros supermassivos com uma massa de milhões de vezes a massa do Sol, localizam-se no coração da maioria das galáxias, incluindo a nossa Via Láctea. Em cerca de 1% dessas galáxias, o buraco negro monstruoso, irradia energia equivalente à bilhões de vezes a energia do Sol, emissões que podem variar em escala de tempo de minutos a anos. Os astrônomos se referem a essas como sendo galáxias ativas.
Mais da metade das fontes de raios-gamma observadas pelo LAT do Fermi, são galáxias ativas, chamadas de blazars, como a PG 1553+113. À medida que a matéria cai em direção ao seu buraco negro supermassivo, algumas partículas subatômicas escapam numa velocidade próxima à velocidade da luz em um par de jatos apontados em direções opostas. O que faz um blazar tão brilhante é que um desses jatos de partículas podem estar diretamente apontados para nós.
Flaring from the_supermassive_black_hole_in_mrk335_studied_with_swift_and_nustarSérgio Sacani
Os comportamentos estranhos e desconcertantes dos buracos negros tornam-se cada dia menos misteriosos, com as novas observações feitas com as missões Swift e NuSTAR da NASA. Os dois telescópios espaciais registraram um buraco negro supermassivo no meio de uma gigantesca explosão de luz de raio-X, ajudando os astrônomos a tentarem resolver um grande quebra-cabeça: Como os buracos negros supermassivos emitem flares?
Os resultados sugerem que os buracos negros supermassivos emitem flares de raios-X, quando suas coroas circundantes, fontes de partículas extremamente energéticas, são atiradas ou lançadas para fora dos buracos negros.
“Essa é a primeira vez que nós somos capazes de linkar o lançamento da coroa com uma flare”, disse Dan Wilkins, da Universidade de Saint Mary em Halifax, no Canadá e principal autor do artigo que descreve os resultados na revista Monthly Notices of The Royal Astronomical Society. “Isso nos ajudará a entender como os buracos negros supermassivos alimentam alguns dos objetos mais brilhantes do universo”.
Os buracos negros supermassivos não emitem luz por si só, mas eles as vezes são circundados por discos de material quente e brilhante. A gravidade do buraco negro puxa o gás ao redor, aquecendo esse material e fazendo com que ele brilhe com diferentes tipos de luz. Outra fonte da radiação perto do buraco negro é a coroa. As coroas são feitas de partículas altamente energéticas que geram luz de raio-X, mas os detalhes sobre sua aparência, ou como elas se formam, ainda não são claros.
This document summarizes observations of the star KIC 8462852 from the Kepler space telescope. Key points:
- Kepler observed irregular dips in the star's brightness up to 22% over its 4-year mission. These dips lasted from 5-80 days and occurred at irregular intervals.
- Follow-up observations characterized KIC 8462852 as a main sequence F3V/IV star with a rotation period of 0.88 days and no significant infrared excess.
- Various scenarios are considered to explain the dips, including dust clumps or exocomet fragments passing in front of the star. The scenario best fitting current data involves a family of exocomet fragments
The vvv survey_reveals_classical_cepheids_tracing_a_young_and_thin_stellar_di...Sérgio Sacani
Com o auxílio do telescópio VISTA instalado no Observatório do Paranal do ESO, astrônomos descobriram uma componente anteriormente desconhecida da Via Láctea. Ao mapear a localização de uma classe de estrelas que variam em brilho chamadas Cefeidas, foi descoberto um disco de estrelas jovens enterradas por trás de espessas nuvens de poeira no bojo central.
O rastreio público do ESO VISTA Variables in the Vía Láctea (VVV) [1] usa o telescópio VISTA instalado no Observatório do Paranal para obter imagens múltiplas em épocas diferentes das regiões centrais da nossa Galáxia nos comprimentos de onda do infravermelho [2]. O rastreio está descobrindo uma enorme quantidade de novos objetos, incluindo estrelas variáveis, aglomerados e estrelas em explosão (eso1101, eso1128, eso1141).
Uma equipe de astrônomos, liderada por Istvan Dékány da Pontificia Universidad Católica de Chile, utilizou dados deste rastreio, obtidos entre 2010 e 2014, para fazer uma descoberta notável — um componente anteriormente desconhecido da Via Láctea, a Galáxia que nos acolhe.
3d modeling of_gj1214b_atmosphere_formation_of_inhomogeneous_high_cloouds_and...Sérgio Sacani
Uma equipe de cientistas da Universidade de Washington e da Universidade de Toronto foram os primeiros a simular nuvens exóticas em 3D na atmosfera de um exoplaneta.
O objeto em questão, é o GJ 1214b, um exoplaneta chamado de mini-Netuno que foi descoberto, seis anos atrás pelos astrônomos no Harvard-Smithsonian Center for Astrophysics.
Também conhecido como Gliese 1214b, esse mundo tem cerca de 2.7 vezes o diâmetro da Terra e uma massa quase 7 vezes maior que a massa do nosso planeta. Ele está localizado a cerca de 52 anos-luz de distância na constelação de Ophiuchus.
O planeta orbita a estrela anã vermelha, GJ 1214, a cada 38 horas, a uma distância de 1.3 milhões de milhas.
De acordo com estudos prévios, o planeta tem uma atmosfera rica em água ou hidrogênio com extensas nuvens.
“Deve existir altas nuvens ou uma névoa orgânica na atmosfera – como nós observamos em Titã. Sua temperatura atmosférica excede o ponto de fusão da água”, disse o Dr. Benjamin Charnay, um dos membros da equipe da Universidade de Washington.
On the theory_and_future_cosmic_planet_formationSérgio Sacani
A Terra chegou cedo para a festa no universo em evolução. De acordo com um novo estudo teórico, quando o nosso Sistema Solar nasceu a 4.6 bilhões de anos atrás, somente 8% dos planetas possivelmente habitáveis que serão formados no universo, existiam. E, a festa não terminaria até quando o Sol queimasse por outros 6 bilhões de anos. A totalidade desses planetas, 92%, não tinham nascido.
Essa conclusão é baseada no acesso dos dados coletados pelo Telescópio Espacial Hubble da NASA e o prolífico caçador de exoplanetas, o Observatório Espacial Kepler.
“Nossa principal motivação foi entender o lugar da Terra no contexto do resto do universo”, disse o autor do estudo Peter Behroozi do Space Telescope Science Institute (STScI), em Baltimore, Maryland, “Comparado a todos os planetas que irão se formar no universo, a Terra, na verdade chegou cedo”.
Olhando distante no espaço e no tempo, o Hubble, tem dado aos astrônomos um verdadeiro “álbum de família”, das observações da galáxia que mostra a história da formação do universo à medida que as galáxias cresciam. Os dados mostram que o universo estava gerando estrelas numa taxa elevada a 10 bilhões de anos atrás, mas a fração do gás hidrogênio e hélio do universo que estava envolvida era muito baixa. Hoje, o nascimento de estrelas está acontecendo numa taxa muito mais lenta do que a muito tempo atrás, mas existe muito gás deixado para trás disponível que o universo continuará gerando estrelas e planetas por muito tempo ainda.
First discovery of_a_magnetic_field_in_a_main_sequence_delta_scuti_star_the_k...Sérgio Sacani
Coralie Neiner do Laboratory for Space Studies and Astrophysics Instrumentation, LESIA (CNRS/Observatoire de Paris/UPMC/Université Paris Diderot) e Patricia Lampens (Royual OIbservatory of Belgium), descobriram a primeira estrela magnética do tipo delta Scuti, através de observações espectropolarimétricas, realizadas com o telescópio CFHT. As estrelas do tipo delta Scuti, são estrelas pulsantes, sendo que algumas delas mostram assinaturas atribuídas para um segundo tipo de pulsação. A descoberta mostra que isso é na verdade a assinatura de um campo magnético. Essa descoberta tem importantes implicações para o entendimento do interior das estrelas.
Dois tipos de estrelas pulsantes existem entre as estrelas com massa entre 1.5 e 2.5 vezes a massa do Sol: as estrelas do tipo delta Scuti e as estrelas do tipo gamma Dor. A teoria nos diz que as estrelas com temperatura entre 6900 e 7400 graus Kelvin podem ter ambos os tipos de pulsação. Essas são então chamadas de estrelas híbridas. Contudo, o satélite Kepler da NASA tem detectado um grande número de estrelas híbridas com temperaturas maiores ou menores do que esse limite pensado anteriormente. A existência dessas estrelas híbridas com temperaturas maiores é algo muito controverso, já que desafia o nosso entendimento sobre as estrelas pulsantes do tipo delta Scuti e gamma Dor.
A higher efficiency_of_converting_gas_to_stars_push_galaxies_at_z_1_6_well_ab...Sérgio Sacani
Galáxias formando estrelas em taxas extremas a nove bilhões de anos atrás eram mais eficientes do que a média das galáxias atuais, descobriram os pesquisadores.
A maioria das estrelas acredita-se localizam-se na sequência principal onde quanto maior a massa da galáxia, mais eficiente ela é na formação de novas estrelas. Contudo, de vez em quando uma galáxia apresentará uma explosão de novas estrelas que brilham mais do que o resto. Uma colisão entre duas grandes galáxias é normalmente a causa dessas fases de explosões de formação de estrelas, onde o gás frio que reside nas grandes nuvens moleculares torna-se o combustível para sustentar essas altas taxas de formação de estrelas.
A questão que os astrônomos têm feito é se essas explosões de estrelas no início o universo foram o resultado de se ter um suprimento de gás abundante, ou se as galáxias convertiam o gás de maneira mais eficiente.
Um novo estudo, publicado no Astrophysical Journal Letters de 15 de Outubro, liderado por John Silverman, do Kavli Institute for Physics and Mathematics of the Universe, estudou o conteúdo do gás monóxido de carbono (CO) em sete galáxias de explosão de estrelas muito distantes, quando o universo tinha apenas 4 bilhões de anos de vida. Isso foi possível devido a capacidade do Atacama Large Millimiter/Submillimiter Array (ALMA), localizado no platô no topo da montanha no Chile, que trabalha para detectar as ondas eletromagnéticas no comprimento de onda milimétrico (importante para se estudar o gás molecular) e um nível de sensibilidade que só agora começa a ser explorado pelos astrônomos.
Os pesquisadores descobriram que a quantidade de gás CO emitido já tinha diminuído, mesmo apesar da galáxia continuar a formar estrelas em altas taxas. Essas observações são similares àquelas registradas para as galáxias de explosões de estrelas próximas da Terra atualmente, mas a quantidade da depleção de gás não foi tão rápida quanto se esperava. Isso levou os pesquisadores a concluírem que poderia haver um contínuo aumento na eficiência, dependendo em de quanto acima da taxa de se formar estrelas ela está da sequência principal.
The neowise discovered_comet_population_and_the_co_co2_production_ratesSérgio Sacani
Após o seu lançamento em 2009, a sonda NEOWISE da NASA já observou 163 cometas durante a missão primária WISE/NEOWISE. Essa amostra do telescópio espacial representa a maior pesquisa infravermelha de cometas já feitas até o momento. Os dados dessa pesquisa estão dando uma nova ideia sobre a poeira, o tamanho dos núcleos do cometa, e a taxa de produção dos gases difíceis de serem observados como dióxido de carbono e monóxido de carbono. Os resultados do censo do NEOWISE dos cometas foram recentemente publicados no Astrophysical Journal.
O monóxido de carbono (CO) e o dióxido de carbono (CO2) são moléculas comuns encontradas no ambiente do início do Sistema Solar, e nos cometas. Na maior parte das circunstâncias, a sublimação do gelo de água provavelmente guia a atividade nos cometas quando eles chegam perto do Sol, mas em distâncias maiores e em temperaturas mais frias, outras moléculas como o CO e o CO2 podem ser os principais guias. O dióxido e o monóxido de carbono são moléculas difíceis de serem detectadas da terra, devido a abundância dessas moléculas na própria atmosfera terrestre que podem obscurecer o sinal. A sonda NEOWISE vaga além da atmosfera da Terra, fazendo essas medidas dos gases emitidos pelos cometas possíveis.
“Essa é a primeira vez que nós observamos essa grande evidência estatística do monóxido de carbono obtida enquanto o gás do cometa é emitido quando ele está mais distante do Sol”, disse James Bauer, vice-principal pesquisador da missão NEOWISE do Laboratório de Propulsão a Jato da NASA em Pasadena, na Califórnia, e autor do artigo. “Emitindo o que é provavelmente monóxido de carbono além de 4 Unidades Astronômicas, ou seja, 600 milhões de quilômetros, isso nos mostra que os cometas podem ter guardado a maior parte dos gases quando eles se formaram, e ficaram ali guardados por bilhões de anos. A maioria dos cometas que nós observamos ativos além das 4 Unidades Astronômicas, são cometas de períodos longos, cometas com períodos orbitais maiores que 200 anos que gastam a maior parte da sua vida além da órbita de Netuno”.
Radio continum emission_of_35_edge_on_galaxies_observed_with_the_vlaSérgio Sacani
Usando um dos maiores rádio observatórios do mundo, o Very Large Array do National Radio Astronomy, um grupo de astrônomos descobriram que os halos ao redor dos discos das galáxias espirais são muito mais comuns do que se pensava anteriormente.
A equipe, dirigida pela Dra. Judith Irwin, da Universidade de Queens, em Kingston, ON, Canadá, observou 35 galáxias espirais próximas de lado, de 11 a 137 milhões de anos-luz de distância da Terra.
As galáxias espirais, como a nossa própria Via Láctea ou a famosa Galáxia de Andrômeda, possuem uma vasta maioria de suas estrelas, gás, e poeira num disco plano em rotação com braços espirais. A maior parte da luz e das ondas de rádio observadas com telescópios veem de objetos localizados nesse disco.
“Nós sabíamos antes que alguns halos existiam, mas, usando o poder total do VLA atualizado e o poder total de algumas técnicas de processamento de imagens, nós descobrimos que esses halos são muito mais comuns entre as galáxias espirais do que nós pensávamos antes”, explicou a Dra. Irwin.
The search for_extraterrestrial_civilizations_with_large_energy_suppliesSérgio Sacani
This document discusses potential signatures that could distinguish transiting megastructures from exoplanets. It identifies nine potential anomalous signatures:
1) Non-disk shapes could produce anomalous transit light curves.
2) Non-gravitational forces could cause orbits inconsistent with the star's density.
3) "Swarms" of many structures could cause irregular or aperiodic transit signals.
4) Structures large enough to completely occult the star could be detected.
5) Very low inferred masses would be anomalous for objects blocking significant starlight.
6) Nearly achromatic eclipses would differ from exoplanets' atmosphere-influenced transits.
Supplementary information spectral_evidence_for_hydrated_salts_on_mars_slopesSérgio Sacani
Novas descobertas feitas pela sonda Mars Reconnaissance Orbiter, a MRO, da NASA fornecem FORTES EVIDÊNICAS de que existe água líquida fluindo atualmente na superfície de Marte. Prestem atenção, não foi detectada água em Marte, não foi, o que foram detectadas foram indicações indiretas de que determinadas feições na superfície marciana podem ser causadas por água fluindo atualmente em sua superfície.
Ah, mas por que isso resolve um grande mistério? Pois, depois de muitas análises, do desenvolvimento de novos algoritmos de análise de imagens e de dados espectrométricos os cientistas puderam definir que as marcas escuras encontradas nos taludes de determinadas crateras podem ser causadas por água salgada fluindo na superfície. Essas marcas já foram identificadas há muitos anos, mas agora, com essas novas técnicas foi possível chegar a essa conclusão.
Usando um espectrômetro de imageamento, a bordo da sonda MRO, os pesquisadores detectaram assinaturas de minerais hidratados nos taludes onde misteriosas listras são vistas no Planeta Vermelho. Essas listras escurecidas aparecem como fluxos e refluxos no passar do tempo. Elas se escurecem e parecem fluir pelos íngremes taludes durante as estações mais quentes, e então se apagam nas estações mais frias. Elas aparecem em alguns locais em Marte quando as temperaturas estão acima de -23 graus Celsius, e desaparecem em épocas mais frias.
O telescópio de rastreio VISTA do ESO encontrou uma horda de galáxias massivas anteriormente ocultas por poeira, que existiram quando o Universo era ainda bebê. Ao descobrir e estudar uma grande quantidade deste tipo de galáxias, os astrônomos descobriram, exatamente e pela primeira vez, quando é que tais monstros apareceram pela primeira vez no Universo.
O simples fato de contar o número de galáxias que existem em determinada área do céu permite aos astrônomos testar teorias de formação e evolução galática. No entanto, uma tarefa aparentemente tão fácil torna-se mais difícil quando tentamos contar galáxias cada vez mais distantes e tênues e é mais complicada ainda devido ao fato das galáxias mais brilhantes e fáceis de observar — as mais massivas no Universo — se tornarem mais raras à medida que os astrônomos observam o passado do Universo, enquanto que as galáxias menos brilhantes, mas muito mais numerosas, são ainda mais difíceis de detectar.
Uma equipe de astrônomos liderada por Karina Caputi do Instituto Astronômico Kapteyn da Universidade de Groningen, descobriu muitas galáxias distantes que não tinham sido detectadas anteriormente. A equipe utilizou imagens do rastreioUltraVISTA, um dos seis projetos que usam o VISTA para mapear o céu no infravermelho próximo, e fez um censo das galáxias tênues quando a idade do Universo estava compreendida entre 0,75 e 2,1 bilhões de anos.
The document discusses key facts and figures about the International Space Station (ISS). It provides statistics on the number of spacewalks, launches, pressurized volume, weight in orbit, meals eaten, lines of code, power generated, and people involved. It lists 59 countries that have participated in ISS utilization and research accomplishments from Expeditions 0-24, including the number of investigations conducted, completed, led by international partners, and from national labs. Scientific publications from research on the ISS are also mentioned.
Astronaut Reid Wiseman tweeted a photo from the International Space Station showing a toy from his childhood floating in space. The document then provides a summary of the most impressive space photos from 2014, including photos taken by Wiseman from the ISS of Earth's landscapes, cities, natural disasters and the moon. It concludes with several close up photos of astronomical objects and phenomena taken by NASA satellites and space telescopes.
Reference Guide To The International Space StationSérgio Sacani
The International Space Station is a unique place – a convergence of science, technology and human innovation that demonstrates new technologies and makes research breakthroughs not possible on Earth.
It is a microgravity laboratory in which an international crew of six people live and work while traveling at a speed of five miles per second, orbiting Earth every 90 minutes.
The space station has been continuously occupied since November 2000. In that time, more than 200 people from 15 countries have visited.
Crew members spend about 35 hours each week conducting research in many disciplines to advance scientific knowledge in Earth, space, physical, and biological sciences for the benefit of people living on our home planet.
The station facilitates the growth of a robust commercial market in low-Earth orbit, operating as a national laboratory for scientific research and facilitating the development of U.S. commercial cargo and commercial crew space transportation capabilities.
More than an acre of solar arrays provide power to the station, and also make it the next brightest object in the night sky after the moon. You don’t even need a telescope to see it zoom over your house. And we’ll even send you a text message or email alert to let you know when (and where) to look up, spot the station, and wave!
First results from_the_hubble_opal_program_jupiter_in_2015Sérgio Sacani
Os cientistas usando o Telescópio Espacial Hubble da NASA/ESA produziram novos mapas de Júpiter, que mostram as contínuas mudanças que ocorrem com a famosa Grande Mancha Vermelha. As imagens também revelam uma rara estrutura em forma de onda na atmosfera do planeta que não tinha sido vista por décadas. A nova imagem é a primeira de uma série de retratos anuais dos planetas externos do Sistema Solar, que nos darão um novo olhar desses mundos remotos, e ajudarão os cientistas a estudarem como eles mudam com o passar do tempo.
Nessa nova imagem de Júpiter, uma grande quantidade de feições foi capturada incluindo ventos, nuvens e tempestades. Os cientistas por trás dessas novas imagens, as obtiveram usando a Wide Field Camera 3 do Hubble, num período de observação de mais de 10 horas e produziram assim dois mapas completos do planeta, a partir das suas observações. Esses mapas fizeram com que fosse possível determinar a velocidade dos ventos em Júpiter, com a finalidade de identificar diferentes fenômenos na sua atmosfera além de traquear as suas feições mais famosas.
As novas imagens confirmam que a grande tempestade que tem existido na superfície de nuvens de Júpiter por no mínimo 300 anos, continua a encolher, mas mesmo que desapareça, ela irá morrer lutando. A tempestade, conhecida como Grande Mancha Vermelha, é vista aqui fazendo seus movimentos em espiral no centro da imagem do planeta. Ela tem diminuído de tamanho de maneira muito rápida de ano em ano. Mas agora, a taxa de encolhimento parece ter reduzido novamente, mesmo apesar da mancha ser cerca de 240 quilômetros menor do que era em 2014.
Dark side of_comet_67_p_churyumov_gerasiemnko_in_august_october_2014Sérgio Sacani
Usando o instrumento Microwave Instrument for Rosetta Orbiter (MIRO), os cientistas estão estudando a região polar sul do cometa no final de sua longa estação de inverno. Os dados sugerem que essas regiões frias e escuras abrigam gelo nas suas primeiras dezenas de centímetros abaixo da superfície em quantidades muito maiores do que as encontradas em outras áreas do cometa.
Desde a sua chegada no Cometa 67P/Churyumov-Gerasimenko, a Rosetta tem pesquisado a superfície e o ambiente desse corpo de forma curiosa. Mas por um longo período de tempo, uma porção do núcleo, as regiões frias e escuras ao redor do polo sul do cometa, permaneceram inacessíveis para quase todos os instrumentos a bordo da sonda.
Devido a uma combinação de sua forma em lobo duplo e a inclinação do seu eixo de rotação, o cometa da Rosetta, tem um padrão sazonal muito peculiar durante a sua órbita de 6.5 anos. As estações estão distribuídas de maneira muito assimétrica entre os dois hemisférios, cada um deles compreende parte tanto dos lobos como do pescoço do cometa.
Na maior parte da órbita do cometa, o hemisfério norte experimenta um verão muito longo, durando cerca de 5.5 anos, e o hemisfério sul passa por um longo, frio e escuro inverno. Contudo, poucos meses antes do cometa passar pelo seu periélio, o ponto na sua órbita, mais próximo do Sol, a situação muda, e o hemisfério sul passa por um breve porém quente verão.
Stellar-like objects with effective temperatures of 2700K and below are referred to as
20 "ultracool dwarfs"1. This heterogeneous group includes both extremely low-mass stars
21 and brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion),
22 and represents about 15% of the stellar-like objects in the vicinity of the Sun2. Based on
23 the small masses and sizes of their protoplanetary disks3,4, core-accretion theory for
24 ultracool dwarfs predicts a large, but heretofore undetected, population of close-in
25 terrestrial planets5, ranging from metal-rich Mercury-sized planets6 to more hospitable
26 volatile-rich Earth-sized planets7. Here we report the discovery of three short-period
27 Earth-sized planets transiting an ultracool dwarf star 12 parsecs away. The inner two
28 planets receive four and two times the irradiation of Earth, respectively, placing them
29 close to the inner edge of the habitable zone of the star8. Eleven orbits remain possible
30 for the third planet based on our data, the most likely resulting in an irradiation
31 significantly smaller than Earth's. The infrared brightness of the host star combined
32 with its Jupiter-like size offer the possibility of constraining the composition and
33 thoroughly characterizing the atmospheric properties of the components of this nearby
34 planetary system, notably to detect potential biosignatures.
Two super-Earths at the edge of the habitable zone of the nearby M dwarf TOI-...Sérgio Sacani
The main scientific goal of TESS is to find planets smaller than Neptune around stars bright enough to allow further characterization studies. Given
our current instrumentation and detection biases, M dwarfs are prime targets to search for small planets that are in (or nearby) the habitable zone
of their host star. Here we use photometric observations and CARMENES radial velocity measurements to validate a pair of transiting planet
candidates found by TESS. The data was fitted simultaneously using a Bayesian MCMC procedure taking into account the stellar variability
present in the photometric and spectroscopic time series. We confirm the planetary origin of the two transiting candidates orbiting around TOI-
2095 (TIC 235678745). The star is a nearby M dwarf (d = 41:90 0:03 pc, Te = 3759 87 K, V = 12:6 mag) with a stellar mass and radius
of M? = 0:44 0:02 M and R? = 0:44 0:02 R, respectively. The planetary system is composed of two transiting planets: TOI-2095b with an
orbital period of Pb = 17:66484 (7 105) days and TOI-2095c with Pc = 28:17232 (14 105) days. Both planets have similar sizes with
Rb = 1:250:07 R and Rc = 1:330:08 R for planet b and c, respectively.We put upper limits on the masses of these objects with Mb < 4:1 M
for the inner and Mc < 7:4 M for the outer planet (95% confidence level). These two planets present equilibrium temperatures in the range of 300
- 350 K and are close to the inner edge of the habitable zone of their star.
This summarizes a scientific study on long-distance quantum teleportation between two laboratories separated by 55 meters but connected by 2 kilometers of fiber optic cable. The key points are:
1) Researchers teleported quantum states (qubits) carried by photons at 1.3 micrometer wavelengths onto photons at 1.55 micrometer wavelengths between the two laboratories.
2) The qubits were encoded in time-bin superpositions and entanglement rather than polarization to make them more robust against decoherence in optical fibers.
3) A partial Bell state measurement was performed using linear optics at the receiving end to probabilistically teleport the quantum states over the long distance.
An earth sized_planet_with_an_earth_sized_densitySérgio Sacani
1) Researchers observed the exoplanet Kepler-78b using the HARPS-N spectrograph to measure its mass.
2) They measured Kepler-78b's mass to be 1.86 Earth masses, giving it a density similar to Earth, implying a rocky composition of iron and rock.
3) The small size of Kepler-78b makes it the smallest exoplanet yet measured for both mass and radius, establishing that Earth-sized planets can be terrestrial.
There are currently 424 known exoplanets orbiting stars other than the Sun. The first exoplanet was discovered in 1992 using pulsar timing and the first using the radial velocity method was 51 Pegasi b in 1995. There are several methods used to detect exoplanets including astrometry, radial velocity, microlensing, timing, and transit. The radial velocity method detects variations in a star's spectral lines caused by the star moving due to gravitational influences from planets. This allows scientists to calculate planetary properties. The transit method detects dips in a star's light curve when a planet passes in front of it, allowing the determination of planetary properties. As of December 2010, there were 510 known planetary systems using various detection methods.
HD 20329b: An ultra-short-period planet around a solar-type star found by TESSSérgio Sacani
This document summarizes the discovery and characterization of HD 20329b, an ultra-short period planet orbiting a solar-type star. Key findings include:
1) HD 20329b was discovered using transit data from the TESS space telescope. It has an orbital period of 0.9261 days.
2) Follow-up observations with HARPS-N measured the planet's mass as 7.42 Earth masses. Its radius is 1.72 Earth radii, giving it a density of 8.06 g/cm3.
3) HD 20329b joins the roughly 30 known ultra-short period planets (orbital period <1 day) that have both mass and radius measurements, helping
A reflective, metal-rich atmosphere for GJ 1214b from its JWST phase curveSérgio Sacani
There are no planets intermediate in size between Earth and Neptune in our Solar System, yet these objects are found around a
substantial fraction of other stars [1]. Population statistics show that
close-in planets in this size range bifurcate into two classes based
on their radii [2, 3]. It is hypothesized that the group with larger
radii (referred to as “sub-Neptunes”) is distinguished by having
hydrogen-dominated atmospheres that are a few percent of the total
mass of the planets [4]. GJ 1214b is an archetype sub-Neptune that
has been observed extensively using transmission spectroscopy to
test this hypothesis [5–14]. However, the measured spectra are featureless, and thus inconclusive, due to the presence of high-altitude
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GJ 1214b Phase Curve 3
aerosols in the planet’s atmosphere. Here we report a spectroscopic thermal phase curve of GJ 1214b obtained with JWST in the
mid-infrared. The dayside and nightside spectra (average brightness
temperatures of 553 ± 9 and 437 ± 19 K, respectively) each show > 3σ
evidence of absorption features, with H2O as the most likely cause in
both. The measured global thermal emission implies that GJ 1214b’s
Bond albedo is 0.51 ± 0.06. Comparison between the spectroscopic
phase curve data and three-dimensional models of GJ 1214b reveal
a planet with a high metallicity atmosphere blanketed by a thick
and highly reflective layer of clouds or haze.
An Earth-sized exoplanet with a Mercury-like compositionSérgio Sacani
Earth, Venus, Mars and some extrasolar terrestrial planets1
have a mass and radius that is consistent with a mass fraction
of about 30% metallic core and 70% silicate mantle2
. At the
inner frontier of the Solar System, Mercury has a completely
different composition, with a mass fraction of about 70%
metallic core and 30% silicate mantle3
. Several formation or
evolution scenarios are proposed to explain this metal-rich
composition, such as a giant impact4, mantle evaporation5
or the depletion of silicate at the inner edge of the protoplanetary
disk6. These scenarios are still strongly debated.
Here, we report the discovery of a multiple transiting planetary
system (K2-229) in which the inner planet has a radius
of 1.165 ± 0.066 Earth radii and a mass of 2.59 ± 0.43 Earth
masses. This Earth-sized planet thus has a core-mass fraction
that is compatible with that of Mercury, although it was
expected to be similar to that of Earth based on host-star
chemistry7
. This larger Mercury analogue either formed with
a very peculiar composition or has evolved, for example, by
losing part of its mantle. Further characterization of Mercurylike
exoplanets such as K2-229 b will help to put the detailed
in situ observations of Mercury (with MESSENGER and
BepiColombo8) into the global context of the formation and
evolution of solar and extrasolar terrestrial planets.
Science with small telescopes - exoplanetsguest8aa6ebb
The search for extrasolar planets has become one of the most attractive problems in modern astrophysics. The biggest observatories in the world are involved in this task as well as little amateur instruments. There is also a huge variety of astronomical methods used for their investigation. Here I present the projects for searching for exoplanets by transit method and our observations of the planet WASP-2b. We observed a transit on 3/4 August 2008 with a 354 mm Schmidt-Cassegrain Celestron telescope and CCD SBIG STL 11000M camera. By precise photometry made using MaximDL software we obtained the light curve of the star system. Decrease of brightness by 0.02m is detected. Analyzing our data we estimate the radius of the planet and inclination of its orbit. Our results are in good correlation with the published information in literature.
This document summarizes the discovery of seven temperate terrestrial planets orbiting the nearby ultracool dwarf star TRAPPIST-1. Through extensive photometric monitoring from both ground-based telescopes and the Spitzer Space Telescope, the researchers detected multiple transiting planets with orbital periods between 1.5 and 12.3 days. Analysis of the transit light curves revealed four additional planets (TRAPPIST-1d, e, f, and g), in addition to the three initially reported. Dynamical modeling suggests the six inner planets have rocky compositions and near-resonant orbits, indicating they likely migrated inward over time. The seven planets have equilibrium temperatures low enough to possibly support liquid water on their surfaces.
A nearby m_star_with_three_transiting_super-earths_discovered_by_k2Sérgio Sacani
This document reports the discovery of three transiting super-Earth planets orbiting a nearby bright M0 dwarf star, EPIC 201367065, using data from the K2 mission. Photometry from K2 reveals three planetary candidates with orbital periods of 10.056, 24.641, and ~45 days and radii between 1.5-2.1 Earth radii. Spectroscopy of the host star determines it has a mass of 0.601 solar masses, radius of 0.561 solar radii, and is located about 45 parsecs away, making the planets some of the coolest small planets known around a nearby star. The system presents an opportunity to measure the planet masses and constrain atmospheric compositions via future observations
Measurement of Jupiter’s asymmetric gravity fieldSérgio Sacani
The gravity harmonics of a fluid, rotating planet can be decomposed
into static components arising from solid-body rotation and dynamic
components arising from flows. In the absence of internal dynamics,
the gravity field is axially and hemispherically symmetric and is
dominated by even zonal gravity harmonics J2n that are approximately
proportional to qn, where q is the ratio between centrifugal
acceleration and gravity at the planet’s equator1
. Any asymmetry in the
gravity field is attributed to differential rotation and deep atmospheric
flows. The odd harmonics, J3, J5, J7, J9 and higher, are a measure of the
depth of the winds in the different zones of the atmosphere2,3
. Here
we report measurements of Jupiter’s gravity harmonics (both even
and odd) through precise Doppler tracking of the Juno spacecraft
in its polar orbit around Jupiter. We find a north–south asymmetry,
which is a signature of atmospheric and interior flows. Analysis of
the harmonics, described in two accompanying papers4,5
, provides
the vertical profile of the winds and precise constraints for the depth
of Jupiter’s dynamical atmosphere.
This document summarizes the discovery and characterization of Kepler-432 b, a massive exoplanet in a highly eccentric orbit around a red giant star. Key findings include:
1) Radial velocity measurements from the CAFE spectrograph revealed Kepler-432 b has a mass of 4.87 ± 0.48 MJup and moves in a highly eccentric orbit (e = 0.535 ± 0.030) around its host star.
2) Simultaneous modeling of Kepler photometry and radial velocity data determined Kepler-432 b has a radius of 1.120 ± 0.036 RJup and orbits every 52.5 days.
3) Analysis of high-resolution images found a nearby star
This document provides information about gravitational fields and Kepler's laws that is relevant to physics exams in Castilla y León, Spain. It includes:
1) Constants related to gravitational fields that are available in PAU exams.
2) Sample problems applying Kepler's laws and Newton's law of universal gravitation to calculate orbital properties of planets, moons, and satellites.
3) Information about gravitational fields near planets and satellites, and how gravitational force and acceleration vary with distance and mass.
This document provides information about constants and laws related to gravitational fields that commonly appear on exams for the PAU (University Access Test) in Castilla y León, Spain. It includes the values of gravitational acceleration on Earth (g0), Earth's radius (RT), Earth's mass (MT), and the gravitational constant (G). It then provides example problems applying Kepler's laws and Newton's law of universal gravitation to calculate orbital properties of planets, moons, and satellites. Sample problems calculate orbital periods, velocities, distances, and gravitational accelerations for bodies in the solar system like Jupiter, Mars, Mercury, the Moon, and artificial satellites.
1) High-dispersion spectroscopy was used to observe the young exoplanet Beta Pictoris b, detecting a blueshifted radial velocity of -15±1.7 km/s and rotational broadening of 25±3 km/s, indicating it spins faster than any planet in the solar system.
2) Beta Pictoris b's high spin velocity is consistent with an extrapolation of the trend of increasing spin velocity with planet mass seen in the solar system.
3) At an estimated age of 11±5 Myr, Beta Pictoris b is expected to cool and shrink over time, which would cause it to spin up further to a rotation velocity of around 40 km/s.
The independent pulsations of Jupiter’s northern and southern X-ray aurorasSérgio Sacani
Jupiter has persistent northern and southern X-ray auroral hot spots observed by XMM-Newton and Chandra observatories. The observations from 2016 and 2007 show that the northern and southern hot spots exhibit different and independent characteristics, such as different periodic pulsations and uncorrelated brightness changes. Mapping of the X-ray emissions indicates they originate from different local time sectors in Jupiter's magnetosphere, beyond 60 Jupiter radii, challenging current models that the hot spots are generated by the same magnetospheric processes.
Using radio observations, astronomers may be able to detect and characterize exoplanets by observing radio emissions from their magnetospheres. Planetary magnetospheres are theorized to produce bursts of decametric radiation through interactions with the solar wind that distort magnetic field lines and accelerate charged particles. While difficult to detect over a host star's emissions, observation of planetary radio signals could provide information on properties like the presence, size, and composition of a magnetosphere, as well as any orbiting satellites. The LOFAR radio telescope may enable the first detections of exoplanetary radio emissions within the next decade.
Artigo que descreve a descoberta do exoplaneta Kepler-432b, um exoplaneta mais massivo que Júpiter que orbita uma estrela gigante vermelha bem próximo e numa órbita extremamente alongada.
Similar to A rocky planet_transiting_a_nearby_low_mass_star (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...
A rocky planet_transiting_a_nearby_low_mass_star
1. A rocky planet transiting a nearby low-mass star
Zachory K. Berta-Thompson1,2, Jonathan Irwin2, David Charbonneau2, Elisa-
beth R. Newton2, Jason A. Dittmann2, Nicola Astudillo-Defru3, Xavier Bonfils4,5,
Michaël Gillon6, Emmanuël Jehin6, Antony A. Stark2, Brian Stalder7, Francois
Bouchy3,8, Xavier Delfosse4,5, Thierry Forveille4,5, Christophe Lovis3, Michel
Mayor3, Vasco Neves9, Francesco Pepe3, Nuno C. Santos10,11, Stéphane Udry3
& Anaël Wünsche4,5
1
Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology,
77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
2
Harvard-Smithsonian Center for Astrophysics,
60 Garden Street, Cambridge, Massachusetts 02138, USA.
3
Observatoire de Genève, Université de Genéve,
51 chemin des Maillettes, 1290 Sauverny, Switzerland.
4
Université Grenoble Alpes, IPAG, F-38000 Grenoble, France.
5
CNRS, IPAG, F-38000 Grenoble, France.
6
Institut d’Astrophysique et de Géophysique, Université de Liège,
Allée du 6 Août 17, Bâtiment B5C, 4000 Liège, Belgium.
7
Institute for Astronomy, University of Hawaii at Manoa,
Honolulu, Hawaii 96822, USA.
8
Laboratoire d’Astrophysique de Marseille, UMR 6110 CNRS, Université de Provence,
38 rue Frédéric Joliot-Curie, 13388, Marseille Cedex 13, France.
9
Departamento de Física, Universidade Federal do Rio Grande do Norte,
59072-970 Natal, Rio Grande do Norte, Brazil.
10
Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto,
CAUP, Rua das Estrelas, 4150-762 Porto, Portugal.
11
Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto,
Rua Campo Alegre, 4169-007 Porto, Portugal.
M-dwarf stars – hydrogen-burning stars that are smaller than
60 per cent of the size of the Sun – are the most common class of
star in our Galaxy and outnumber Sun-like stars by a ratio of 12:1.
Recent results have shown that M dwarfs host Earth-sized plan-
ets in great numbers1,2: the average number of M-dwarf planets
that are between 0.5 to 1.5 times the size of Earth is at least 1.4 per
star3. The nearest such planets known to transit their star are 39
parsecs away4, too distant for detailed follow-up observations to
measure the planetary masses or to study their atmospheres. Here
we report observations of GJ 1132b, a planet with a size of 1.2 Earth
radii that is transiting a small star 12 parsecs away. Our Doppler
mass measurement of GJ 1132b yields a density consistent with
an Earth-like bulk composition, similar to the compositions of the
six known exoplanets with masses less than six times that of the
Earth and precisely measured densities5−11. Receiving 19 times
more stellar radiation than the Earth, the planet is too hot to be
habitable but is cool enough to support a substantial atmosphere,
one that has probably been considerably depleted of hydrogen. Be-
cause the host star is nearby and only 21 per cent the radius of the
Sun, existing and upcoming telescopes will be able to observe the
composition and dynamics of the planetary atmosphere.
arXiv:1511.03550v1[astro-ph.EP]11Nov2015
2. a rocky planet transiting a nearby low-mass star 2
We used the MEarth-South telescope array12 to monitor the bright-
ness of the star GJ 1132, starting on 28 January 2014. The array con-
sists of eight 40-cm robotic telescopes located at the Cerro Tololo
Inter-American Observatory (CTIO) in Chile, and observes a sample
of M-dwarf stars that are within 33 parsecs of Earth and smaller than
0.35 Solar radii. Since early 2014, the telescopes have gathered data
almost every night that weather has permitted, following a strategy
similar to that of the MEarth-North survey13. On 10 May 2015, GJ
1132 was observed at 25-minute cadence until a real-time analysis
system identified a slight dimming of the star indicative of a possible
ongoing transit, and commanded the telescope to observe the star
continuously at 0.75-minute cadence. These triggered observations
confirmed the presence of a transit with a sharp egress (Fig. 1).
0.995
1.000
MEarth
discovery
E=-19 (1xMEarth)
0.995
1.000
MEarth
follow-up
E=-11 (4xMEarth), E=0 (4xMEarth), E=11 (4xMEarth)
0.995
1.000
TRAPPIST
E=0
0.995
1.000
PISCOg'
E=0
0.04 0.02 0.00 0.02 0.04
Phased time from mid-transit (days)
0.995
1.000
PISCOi'
E=0
Relativebrightness
Figure 1: Photometric measurements
of transits of GJ 1132b. Light curves
from the MEarth-South, TRAPPIST and
PISCO telescopes/imagers were fitted
with a transit model (grey lines) and
a Gaussian process noise model (sub-
tracted from this plot), and averaged
to 1.5-min bins for visual clarity. For
MEarth-South, both the initial triggered
‘discovery’ observations and the sub-
sequent ‘follow-up’ observations are
shown. Labels indicate the transit event
(with E as an integer number of plan-
etary periods) and, for MEarth-South,
the number of telescopes used. The
opacities of binned points are inversely
proportional to their assigned vari-
ances, representing their approximate
weights in the model fit. The raw data
and details of the fit are presented in
Methods; g and i refer to the wave-
length bandpasses used from the PISCO
imager.
3. a rocky planet transiting a nearby low-mass star 3
A search of extant data (4,208 observations over 333 nights) for
periodic signals revealed a 1.6-day candidate that included this event
and reached a detection statistic13 of 9.1σ. Follow-up photometry of
subsequent predicted transits with four MEarth-South telescopes, the
TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope)
telescope14, and the PISCO (Parallel Imager for Southern Cosmology
Observations) multiband imager15 on the Magellan Clay telescope
confirmed the transit signal as being consistent with a planet-sized
object blocking 0.26% of the star’s light. We began precise Doppler
monitoring with the HARPS (High Accuracy Radial Velocity Planet
Searcher) spectrograph16 on 6 June 2015 and gathered 25 radial veloc-
ity measurements for determining the planetary mass (Fig. 2).
Figure 2: Radial velocity changes over
the orbit of GJ 1132b. Measurements
of the star’s line-of-sight velocity,
taken by the HARPS spectrograph, are
shown phased to the planetary orbital
period determined from the light
curves (orange points, with duplicates
shown in grey). Error bars correspond
to 1σ. The darkness of each point is
proportional to its weight in the model
fit, which is the inverse of its variance
as predicted by a radial velocity noise
model. For a circular orbit, the star’s
reflex motion to the planet has a semi-
amplitude of K = 2.76 ± 0.92 m s−1.
The distance to GJ 1132 has been measured through trigonometric
parallax to be 12.04 ± 0.24 parsecs17, a value that we independently
validate with MEarth astrometry (see Methods). Together with em-
pirical relations among the intrinsic luminosities, masses and radii
of M-dwarf stars18,19, the parallax enables us to estimate the mass
and radius of GJ 1132. These estimates are not biased by physically
associated luminous companions, which are ruled out by published
photometry results and the HARPS spectra. Likewise, unassociated
background stars are too faint in archival imaging at the current sky
position of this high-proper-motion star to corrupt our estimates of
the stellar parameters. Table 1 presents the physical properties of the
star (GJ 1132) and planet (GJ 1132b), combining the inferred stellar
properties with analyses of the transit light curves (Fig. 1) and radial
velocity observations (Fig. 2). The radius of the planet is 40% that of
GJ 1214b (ref. 20), a well studied mini-Neptune exoplanet that orbits
with a similar period around a similar host star.
4. a rocky planet transiting a nearby low-mass star 4
Table 1: System properties for GJ 1132b
Parameter Value
Stellar parameters
Photometry V = 13.49, J = 9.245, K = 8.322
Distance to star, D 12.04 ± 0.24 parsecs
Mass of star, M 0.181 ± 0.019M
Density of star, ρ 29.6 ± 6.0 g cm−3
Radius of star, R 0.207 ± 0.016R
Luminosity of star, L 0.00438 ± 0.00034L
Effective temperature, Teff 3270 ± 140 K
Metallicity, [Fe/H] −0.12 ± 0.15
Age of star, τ > 5 Gyr
Transit and radial velocity parameters
Orbital period, P (days) 1.628930 ± 0.000031
Time of mid-transit, t0 (BJDTDB; days) 2457184.55786 ± 0.00032
Eccentricity, e 0 (fixed)
Planet-to-star radius ratio, Rp/R 0.0512 ± 0.0025
Scaled orbital distance, a/R 16.0 ± 1.1
Impact parameter, b 0.38 ± 0.14
Radial velocity semi-amplitude, K 2.76 ± 0.92 m s−1
Systemic velocity, γ +35 ± 1 km s−1
Planet parameters
Radius of planet, Rp 1.16 ± 0.11R⊕
Mass of planet, Mp 1.62 ± 0.55M⊕
Density of planet, ρp 6.0 ± 2.5 g cm−3
Surface gravity on planet, gp 1170 ± 430 cm s−2
Escape velocity, Vesc 13.0 ± 2.3 km s−1
Equilibrium temperature, Teq
assuming Bond albedo of 0.00 579 ± 15 K
assuming Bond albedo of 0.75 409 ± 11 K
Transit and radial velocity parameters were estimated from a Markov chain
Monte Carlo (MCMC) analysis, including an external constraint on the stellar
density when deriving P, t0, Rp/R , a/R , and b (see Methods). Planetary
properties were derived from the combined stellar, transit, and radial velocity
parameters. L , luminosity of the Sun; M , mass of the Sun; R , radius of
the Sun; BJDTDB, Barycentric Julian Date in the Barycentric Dynamical Time
system; a, orbital semimajor axis; M⊕, mass of Earth; R⊕, radius of Earth.
5. a rocky planet transiting a nearby low-mass star 5
GJ 1132b’s average density resembles that of the Earth, and is well
matched by a rock/iron bulk composition. A theoretical mass-radius
curve21 for a two-layer planet composed of 75% magnesium silicate
and 25% iron (by mass) is consistent with our estimates for GJ 1132b
(Fig. 3). This model assumes that the core is pure iron, the mantle is
pure magnesium silicate, and the interior contains no water21. These
simplifications mean that the iron fraction should not be taken as ab-
solute; the model simply represents a characteristic mass-radius locus
that matches Earth and Venus. This same composition also matches
the masses and radii of Kepler-78b (refs 8, 9), Kepler-10b (ref. 7),
Kepler-93b (ref. 10), Kepler-36b (ref. 6), CoRoT-7b (ref. 5), and HD
219134b (ref. 11) to within 1σ. All of these planets are smaller than
1.6 Earth radii, a transition radius above which most planets require
thick hydrogen/helium envelopes to explain their densities22. At the
1σ lower bound of GJ 1132b’s estimated mass, models23 indicate that
replacing only 0.2% of the rock/iron mix with a hydrogen/helium
layer would increase the planet’s radius to 1.4 times that of the Earth,
substantially larger than the observed value. Detection of GJ 1132b’s
mass is currently only at the 3σ level, but continued Doppler moni-
toring will shrink the 35% mass uncertainty and enable more detailed
comparison with other planets and compositional models.
We searched for additional planets both as other transits in the
MEarth-South light curve and as periodic signals in the HARPS
residuals. Although we made no notable discoveries, we highlight
that compact, coplanar, multiple-planet systems are common around
small stars24,25. Further exploration of the GJ 1132 system could
reveal more, potentially transiting, planets.
As a relatively cool rocky exoplanet with an equilibrium tem-
perature between 580 K (assuming a Bond albedo of 0) and 410 K
(assuming a Venus-like Bond albedo of 0.75), GJ 1132b may have re-
tained a substantial atmosphere. At these temperatures, the average
thermal speeds of atoms or molecules heavier than helium are less
than one-eighth of the escape velocity, suggesting an atmosphere
could be stable against thermal escape. This is not the case for the
other rocky exoplanets for which precise densities are known, all
of which are considerably hotter. The rocky planet Kepler-78b (refs
8, 9), which is comparable in size and density to GJ 1132b, receives
200 times more irradiation than GJ 1132b. Whether the atmosphere
of GJ 1132b was initially dominated by hydrogen/helium-rich gas
accreted from the primordial nebula or by volatiles outgassed from
the planetary interior, its composition probably evolved substantially
over the age of the system, which we estimate to exceed 5 billion
years (gigayears, Gyr) (see Methods). Irradiated well beyond the
runaway greenhouse limit26, surface water would extend up to high
6. a rocky planet transiting a nearby low-mass star 6
Figure 3: Masses, radii, and distances
of known transiting planets. a, The
radius and mass of GJ 1132b (orange)
are shown, along with those of other ex-
oplanets (grey). Also shown are mass-
radius curves predicted by theoretical
models21 for planets composed of 100%
H2O (blue line), and for two-component
planets composed of MgSiO3 on top
of Fe cores that are 0% (light brown),
25% (darker brown) or 50% (red) of the
total mass. Planets with smaller frac-
tional mass and radius uncertainties are
darker. b, Symbol area is proportional
to transit depth. In comparison with
other transiting exoplanets, those with
masses detected at > 2.5σ (black) and
those without masses detected at such
level (blue), GJ 1132b is the most acces-
sible terrestrial planet for spectroscopic
observations of its atmosphere, owing
to the proximity and small size of its
parent star.
altitudes where it could be destroyed by photolysis and its hydrogen
rapidly lost to space. When the star was young and bright at ultravi-
olet wavelengths, an atmosphere with high concentrations of water
could lose hydrogen at the diffusion limit, of the order of 1013 atoms
per cm2 per second or 10 Earth oceans per gigayear. Depending on
surface weathering processes, the oxygen left behind might persist as
O2 in the atmosphere26,27. In this scenario, water would constitute a
trace component in an atmosphere otherwise dominated by O2, N2,
and CO2. However, large uncertainties in the size of the initial hydro-
gen reservoir, in the history of the star’s ultraviolet luminosity, in the
contribution of late volatile delivery, and in the evolutionary effect of
the system’s likely spin-orbit synchronization preclude firm a priori
statements about the composition of the atmosphere.
Future spectroscopic investigation of the planetary atmosphere
will be enabled by the proximity and small radius of the star. When
viewed in transmission during transit, one scale height of an O2-rich
atmosphere would overlap 10 parts per million (p.p.m.) of the stellar
disk. For comparison, a 60-orbit Hubble Space Telescope transmis-
sion spectrum of GJ 1214b achieved a transit depth precision of 25
p.p.m. in narrow wavelength bins28. Deeper Hubble observations of
GJ 1132, which is 50% brighter than GJ 1214, would have the poten-
tial to detect molecular absorption features in GJ 1132b’s atmosphere.
Observations with the James Webb Space Telescope (JWST), set to
launch in 2018, could measure the transmission spectrum over a
broader wavelength range and require less telescope time. The long-
7. a rocky planet transiting a nearby low-mass star 7
wavelength capabilities of JWST may also allow it to detect the ther-
mal emission from the planet; such emission represents 40-130 p.p.m.
of the system flux at a wavelength of 10 µm, and 160-300 p.p.m. of
the flux at 25 µm (for the range of albedos considered above). Pro-
vided that the planet is not too cloudy, combined transmission and
emission spectra could ascertain the abundances of strongly absorb-
ing molecular species. If such constraints on the dominant infrared
opacity sources can be obtained, observations of the planet’s ther-
mal phase curve would be sensitive to complementary information,
including the total atmospheric mass29,30. Such observations will in-
form our understanding of how the strong tides and intense stellar
activity of the M-dwarf planetary environment influence the evolu-
tion of terrestrial atmospheres. This understanding will be important
for the long-term goal of looking for life on planets orbiting nearby
small stars.
Received 3 August; accepted 23 September 2015; doi:10.1038/nature15762.
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Supplementary Information is available in the online version of the paper.
Acknowledgements We thank the staff at the Cerro Tololo Inter-American Observatory
for assistance in the construction and operation of MEarth-South; J. Winn and J. Berta-
Thompson for comments on the manuscript; S. Seager and A. Zsom for conversations
that improved the work; L. Delrez for her independent analysis of the TRAPPIST data;
and J. Eastman, D. Dragomir and R. Siverd for their efforts to observe additional tran-
sits. The MEarth Project acknowledges funding from the David and Lucile Packard
Fellowship for Science and Engineering, and the National Science Foundation, and a
grant from the John Templeton Foundation. The opinions expressed here are those of
the authors and do not necessarily reflect the views of the John Templeton Founda-
tion. The development of the PISCO imager was supported by the National Science
Foundation. HARPS observations were made with European Space Observatory (ESO)
Telescopes at the La Silla Paranal Observatory. TRAPPIST is a project funded by the
Belgian Fund for Scientific Research, with the participation of the Swiss National
Science Foundation. Z.K.B.-T. is funded by the MIT Torres Fellowship for Exoplanet
9. a rocky planet transiting a nearby low-mass star 9
Research. X.B., X.D., T.F. and A.W. acknowledge the support of the French Agence
Nationale de la Recherche and the European Research Council. M.G. and E.J. are FNRS
Research Associates. V.N. acknowledges a CNPq/BJT Post-Doctorate fellowship and
partial financial support from the INCT INEspaço. N.C.S. acknowledges the support
from the Portuguese National Science Foundation (FCT) as well as the COMPETE
program.
Author Contributions The MEarth team (D.C., J.I., Z.K.B.-T., E.R.N. and J.A.D.) dis-
covered the planet, organized the follow-up observations, and led the analysis and
interpretation. Z.K.B.-T. analysed the light curve and radial velocity data, and wrote
the manuscript. J.I. designed, installed, maintains, and operates the MEarth-South tele-
scope array, identified the first triggered transit event, and substantially contributed to
the analysis and interpretation. D.C. leads the MEarth Project, and assisted in analysis
and writing the manuscript. E.R.N. determined the metallicity, kinematics, and rota-
tion period of the star. J.A.D. confirmed the star’s trigonometric parallax and helped
install the MEarth-South telescopes. The HARPS team (N.A.-D., X.B., F.B., X.D., T.F.,
C.L., M.M., V.N., F.P., N.C.S., S.U. and A.W.) obtained spectra for Doppler velocime-
try, with N.A.-D. and X.B. leading the analysis of those data. M.G. and E.J. gathered
photometric observations with TRAPPIST. A.A.S. and B.S. gathered photometric obser-
vations with PISCO. All authors read and discussed the manuscript.
Author Information Reprints and permissions information is available at http:
//www.nature.com/reprints. The authors declare no competing financial interests.
Readers are welcome to comment on the online version of the paper. Correspondence
and requests for materials should be addressed to Z.K.B.-T. (zkbt@mit.edu).
Methods
Distance to the star GJ 1132’s coordinates are 10:14:51.77 -47:09:24.1
(International Celestial Reference System, epoch 2000.0), with proper
motions of (-1046; 416) milliarcseconds (mas) per year and a trigono-
metric parallax of π = 83.07 ± 1.69 mas, as determined by the RE-
CONS (Research Consortium on Nearby Stars) survey17. We qual-
itatively confirm this parallax with independent observations from
MEarth-South, using analyses like those that have been applied to
the northern survey31. The motion of GJ 1132 relative to background
stars in MEarth-South imaging closely matches the prediction made
by the RECONS parallax (Extended Data Fig. 1). We do not quote the
value of π derived from MEarth-South because we have not yet cross-
validated the astrometric performance of the system against other
measurements. Literature photometric observations of GJ 1132 in-
clude photoelectric photometry (U = 16.51 ± 0.03, B = 15.17 ± 0.03)32,
charge-coupled device (CCD) photometry (V = 13.49 ± 0.03,
RC = 12.26 ± 0.02, IC = 10.69 ± 0.02)17, 2MASS near-infrared photom-
etry (J = 9.245 ± 0.026, H = 8.666 ± 0.027, Ks = 8.322 ± 0.027)33, and
WISE infrared photometry (W1 = 8.170 ± 0.023, W2 = 8.000 ± 0.020,
W3 = 7.862 ± 0.018, W4 = 7.916 ± 0.184). The colour (V − Ks =
5.168 ± 0.040) and absolute magnitude (MV = 13.088 ± 0.054) of GJ
1132 are consistent with those of single M4V dwarfs34.
Extended Data Figure 1: Astrome-
try of GJ 1132 from MEarth-South.
Measurements of the star GJ 1132’s
position in MEarth-South images, along
the directions of ecliptic latitude (top)
and longitude (bottom). As described
elsewhere31, a fitted offset between
data gathered at a field rotation of 0◦
(blue) and 180◦ (green) has been re-
moved. The published RECONS proper
motion17 has been subtracted, and a
model fixed to the published 83.07 mas
parallax (black line) closely matches the
MEarth-South observations.
10. a rocky planet transiting a nearby low-mass star 10
Metallicity of the star Before discovering the planet, we gathered a
near-infrared spectrum of GJ 1132 with the FIRE spectrograph on the
Magellan Baade telescope. We shifted the spectrum to a zero-velocity
wavelength scale35, measured equivalent widths and compared the
spectra by eye with solar metallicity spectral type standards35. The
spectrum indicates a near-infrared spectral type of M4V-M5V (Ex-
tended Data Fig. 2), slightly later than the optical spectral of M3.5V
listed in the PMSU (Palomar/Michigan State University) catalogue36.
Using the measured equivalent width of the K-band sodium feature
(4.7Å) and an empirical calibration35 that has been corrected for its
known temperature dependence37, we estimate the stellar metallicity
to be [Fe/H] = −0.12 ± 0.15 and quote this value in Table 1. For com-
parison, a relation using additional spectral regions and calibrated
for stars of GJ 1132’s spectral type and earlier38 also yields [Fe/H] =
-0.1, while one for GJ 1132’s spectral type and later39 yields [Fe/H] =
-0.2 (both with uncertainties of about 0.15 dex).
Extended Data Figure 2: Near-infared
spectrum of GJ 1132. Observations of
GJ 1132’s spectrum obtained with the
FIRE spectrograph on the Magellan
Baade telescope are compared in the
z, J, H and K telluric windows (left
to right, top to bottom) to the solar-
metallicity composite spectral type
standards from ref. 35. The FIRE spec-
tra have been smoothed to match the
R = 2, 000 resolution of the standards.
GJ 1132’s near-infrared spectral type is
M4V-M5V.
Mass of the star Dynamical mass measurements of M-dwarfs show
that tight relationships exist between near-infrared absolute mag-
nitudes and stellar mass18. We use these calibrations to calculate
masses from the J, H and K magnitudes (after converting between
the 2MASS and CIT photometric systems). Taking the mean of these
masses and adopting an uncertainty that is the quadrature sum of the
2.7% error propagated from the measurement uncertainties and the
10% scatter we assume for the relations, we adopt a stellar mass of
M = 0.181 ± 0.019M , where M is the mass of the star and M is
the mass of the Sun.
11. a rocky planet transiting a nearby low-mass star 11
Radius of the star From this mass, we use an empirical M − ρ
relation19 calibrated to eclipsing binary systems to estimate a density
of ρ = 29.6 ± 6.0 g cm−3, corresponding to R = 0.207 ± 0.016R
for GJ 1132. We adopt those values, noting that they agree with two
other mass-radius relations: the radius predicted by long-baseline op-
tical interferometry of single stars40 is R = 0.211 ± 0.014R , and that
by the Dartmouth evolutionary models41 is R = 0.200 ± 0.016R (for
[Fe/H] = -0.1, assuming a uniform prior on age between 1 Gyr and
10 Gyr). The quoted errors do not include an assumed intrinsic scat-
ter in any of the mass–radius relations, but the consistency among
the three estimates suggests that any contribution from scatter would
be smaller than the uncertainty propagated from the stellar mass.
Bolometric luminosity of the star We combine the parallax and pho-
tometry with bolometric corrections to determine the total lumi-
nosity of GJ 1132, testing three different relations to estimate bolo-
metric corrections from colour. The Mann et al. relation42 between
BCV and V − J colour yields a bolometric luminosity of 0.00402L .
The Leggett et al. relation43 between BCK and I − K colour yields
0.00442L . The Pecaut and Mamajek compilation of literature bolo-
metric corrections44, when interpolated in V − Ks colour to determine
BCV, yields 0.00469L . We adopt the mean of these three values,
with an uncertainty that is the quadrature sum of the systematic er-
ror (the 6.3% standard deviation of the different estimates) and the
uncertainty propagated from the measurement uncertainties (about
5% in all three cases), as our final estimate of the bolometric lumi-
nosity: L = 0.00438 ± 0.00034L . From this, we calculate the stellar
effective temperature as Teff = 5772K × (L /L )1/4 × (R /R )−1/2 =
3270 ± 140K. The luminosity and temperature we infer37 from the
FIRE spectra (L = 0.0044 ± 0.001L , Teff = 3130 ± 120K) are consis-
tent with the quoted values.
Extended Data Figure 3: Photometric
starspot modulations of GJ 1132.
MEarth-South photometry (with dots
representing single pointings and error
bars representing ±1σ uncertainty
ranges on weighted averages over
four-day bins) probes starspots that
are rotating in and out of view, and
indicates that GJ 1132 has a rotation
period of approximately 125 days. The
rotational modulation was identified
using a methodology similar to that
used in previous MEarth work48.
∗UVW velocities have been updated to use the proper motion
stated above. The values given in the published article were
based on the proper motion from ref. 64, and were also
with respect to the local standard of rest. We adopt the solar
velocities of ref. 65.
Age of the star GJ 1132’s motion through the Galaxy of (ULSR, VLSR,
WLSR) = (-47, -32, -2) km s−1 is consistent with a kinematically older
stellar population∗. M4 dwarfs tend to show strong Hα emission for
about 4 Gyr45; the lack of Hα emission in the HARPS spectrum indi-
cates that GJ 1132 is probably older than that. The star instead shows
weak Hα absorption, which is an indicator of non-zero magnetic ac-
tivity in stars as cool as this46. We detect emission in the Ca II H line,
with a weak intensity that is comparable to that of Barnard’s Star and
other slowly rotating stars in the HARPS M-dwarf sample47. Apply-
ing published methods48 to the MEarth-South photometry, we mea-
sure a rotation period of 125 days for GJ 1132 (Extended Data Fig.
3). M-dwarfs spin more slowly as they age, with less massive stars
12. a rocky planet transiting a nearby low-mass star 12
reaching longer rotation periods at old ages48. Therefore, the rotation
period suggests that the system could be almost as old as Barnard’s
Star (0.16 M ), which has a 130-day rotation period49 and is 7-13 Gyr
old50. GJ 1132’s age is probably comparable to or greater than that
of Proxima Centauri (0.12 M ), which has an 83-day period49,51 and
is 5-7 Gyr old, assuming it to be coeval with the gyrochronologically
and asteroseismically age-dated α Centauri system52. From these
comparisons, we conclude that GJ 1132 is probably older than 5 Gyr.
Assumption of a circular orbit Calculating the timescale for tidal
circularization53 as tcirc = 2PQ
63π ×
Mp
M × a
Rp
5
, assuming a tidal
quality factor of Q = 100 appropriate for rocky exoplanets, yields
4 × 105 years for GJ 1132b. This is much shorter than the age of the
system; therefore, we assume the eccentricity to be negligible and fix
it to 0 in our estimation of the other planetary properties. Perturba-
tions from other (undetected) planets in the system could potentially
induce a small equilibrium eccentricity.
Photometric observations and analysis The high-cadence light curves
analysed here were gathered over four nights using six telescopes on
three mountains. The triggered event (event E = −19, relative to the
ephemeris in Table 1) was collected on MEarth-South telescope 3. At
the time of this triggered detection, 296 stars in the MEarth-South
sample had been observed at least 100 times, but only nine of these
stars had been observed as thoroughly as GJ 1132. After identifica-
tion of the periodic signal, we obtained follow-up photometry with
MEarth-South telescopes 2, 3, 4 and 8 on the nights of 23 May 2015,
10 June 2015 and 28 June 2015 (E = −11, 0 and 11). Exposure times
were 18 s, yielding a 47-s cadence for the high-cadence light curves.
We observed the transit on the night of 10 June 2015 (E = 0) with
the TRAPPIST telescope, in a wide I + z bandpass, with exposure
times of 10 s and a cadence of 21 s. We also observed this transit with
the PISCO multiband imager, which was installed on the Magellan
Baade telescope and undergoing a commissioning run, taking 10-s
exposures simultaneously in g , r , i , z bandpasses at a cadence of
36 s. We actively defocused Baade, resulting in donut-shaped point
spread functions spreading each star’s light over about 200 pixels.
The PISCO r and z light curves exhibited unexplained systematics
and were not used for further analysis.
To the high-cadence light curves, we fitted a transit model54 with
the following parameters: orbital period P, time of mid-transit t0,
planet-to-star radius ratio Rp/R , star-to-orbit radius ratio R /a, im-
pact parameter b, and separate baseline flux levels for each transit
observed on each telescope. The PISCO and TRAPPIST photome-
13. a rocky planet transiting a nearby low-mass star 13
try showed trends that correlated with airmass, so we also included
coefficients for a trend linear with airmass as free parameters. Limb-
darkening was treated with a quadratic approximation, using fixed
coefficients55 calculated from a PHOENIX atmosphere model for a
3,300 K, [Fe/H] = 0, log g = 5 star. These coefficients (u1, u2) were:
(0.1956, 0.3700) for MEarth and TRAPPIST (both approximated as
1
3 i + 2
3 z ), (0.4790, 0.3491) for PISCO g (approximated as Sloan g ),
and (0.2613,0.3737) for PISCO i (approximated as Sloan i ). We per-
formed a Levenberg-Marquardt maximization of the posterior proba-
bility of this model, rejected > 4σ outliers among the data, repeated
the maximization, and increased the per-point uncertainty estimates
until each transit exhibited a reduced χ2 ≤ 1. This resulted in typical
per-point uncertainties of 2.6 (MEarth), 3.6 (TRAPPIST), 1.9 (PISCO
g ), and 1.2 (PISCO i ) mmag. Most light curves showed some ev-
idence for time-correlated noise in their residuals. To marginalize
over the uncertainty introduced by these correlations, we use the
Gaussian process regression package George56 to model each set of
transit residuals as a Gaussian process with non-zero covariance be-
tween the datapoints57. We use a Matérn-3/2 kernel function to de-
scribe this covariance as a function of separation in time, and include
two free parameters per transit: log tgp (where tgp is the correlation
timescale) and log agp (where agp is an amplitude). We mapped the
probability distribution of the model parameters using the emcee
implementation58 of an affine-invariant Markov chain Monte Carlo
(MCMC) sampler59, assuming flat priors on all parameters. Extended
Data Fig. 4 shows raw light curves of individual transits, along with
model curves sampled from the posterior.
The ingress time (τ = 3.7 ± 1.0 min from first to second contact)
is measured imprecisely in this fit, compared to the total transit du-
ration (Ttot = 47.0 ± 1.4 min from first to fourth contact). Systematic
astrophysical errors (incorrect limb-darkening, starspots, unidentified
transit timing variations) can bias light-curve estimates of the ingress
time, and therefore also the parameters R /a and b that depend
strongly on τ. Therefore, we estimate the planet properties without
relying on this ingress measurement, by including external con-
straints on both the stellar mass and the stellar density. We sample
values of M and ρ from Gaussian distributions (0.181 ± 0.019M
and 29.6 ± 6.0 g cm−3), use Kepler’s Third Law to compute R /a
from the stellar density and the period, and then calculate b from
the transit duration and these new R /a samples. We quote the
marginalized values and uncertainties for these and other light-curve
parameters in Table 1. This procedure forces consistency between
the light-curve fit and the inferred stellar properties and shifts the
estimates from R /a = 0.0738 ± 0.0092 and b = 0.58 ± 0.14 (inferred
14. a rocky planet transiting a nearby low-mass star 14
from the light curves alone) to the values in Table 1. The effect on
P, t0, or Rp/R is negligible. If we ignore the external ρ informa-
tion, the inferred stellar and planetary radii would be consistent with
those in Table 1 but with larger error bars (R = 0.243 ± 0.031R and
Rp = 1.37 ± 0.22R⊕).
Extended Data Figure 4: Raw transit
light curves of GJ 1132b. Light curves
are shown both unbinned (grey points)
and in five-minute bins (black bars,
representing the ±1σ uncertainty
range for the weighted average in each
bin), and separated by telescope (row)
and transit event (column). Model
curves are shown, with the Gaussian
process noise model conditioned on the
observations, for parameters sampled
from the posterior (green) and for the
maximum likelihood parameters (blue).
This is the complete set of light-curve
data behind the transit parameter fits.Radial velocity observations and analysis We first gathered reconnais-
sance spectra of GJ 1132 with the CHIRON60 spectrograph on the
SMARTS 1.5-metre telescope at CTIO. Once these spectra ruled out
large radial-velocity variations corresponding to binary star compan-
ions, we began observations with the HARPS spectrograph on the
La Silla 3.6-metre telescope. We gathered 25 HARPS spectra of GJ
1132 between 6 June 2015 and 18 July 2015, using an exposure time of
40 min. The spectra span 380 nm to 680 nm in wavelength. For each
observation, we constructed a comparison template by co-adding all
the other spectra and measured the relative radial velocity as the shift
required to minimize the χ2 of the difference between the spectrum
15. a rocky planet transiting a nearby low-mass star 15
and this template61,62. Telluric lines were masked using a template
of lines made with a different, much larger, data set. We see no ev-
idence for rotational broadening of the spectra, indicating that the
projected rotational velocity, v sin i, is less than 2 km s−1
. The median
of the internal radial velocity uncertainty estimates61 is 3 m s−1 per
observation.
Over the timespan of our observations, these radial velocities are
dominated by the orbital motion of the known transiting planet,
rather than by other planets, blended stellar binaries, or stellar ac-
tivity. The tallest peak in the periodogram of the radial velocities is
consistent with the transit-derived period for GJ 1132b. The line bi-
sectors show no significant correlation with the measured velocities
(Pearson correlation p-value of 0.27) and no clear periodicities. The
Hα equivalent width and the full-width half-maximum of the HARPS
cross-correlation function are not correlated with the velocities (Pear-
son correlation p-values of 0.72 and 0.57).
We fit the velocities with a model corresponding to a circular orbit
for the planet, with flat priors on three free-floating parameters: the
radial velocity semi-amplitude K , the systemic velocity γ , and a
stellar jitter term σ ,jitter that is added in quadrature to the internal
velocity uncertainties. We include all terms that depend on σ ,jitter
in the likelihood, as well as the usual χ2 term. P and t0 were fixed
to the values determined from the transit analysis. We use emcee58
to sample from the posterior probability distributions of these pa-
rameters, and quote marginalized uncertainties on K in Table 1. In
this fit, the value of K is > 0 in 99.7% of the MCMC samples. The
inferred value of σ ,jitter is smaller than the individual uncertainties
(< 1.9 m s−1 at 68% confidence), and a good fit is obtained if σ ,jitter
is fixed to 0 (χ2 = 26.67 for 23 degrees of freedom). The χ2 of a fit
where both K and σ ,jitter are fixed to 0 is significantly worse (38.56
for 24 degrees of freedom). As a check, we repeated the MCMC fit
allowing the phase (t0) to float. This radial velocity fit predicted the
known mid-transit times to within 1.5σ (3.0 ± 1.9 h after the true
transit times). Relaxing the assumption of a circular orbit yields in-
ferred distributions of (e cos ω, e sin ω) that are consistent with (0,
0) but substantially increases the uncertainty on the semi-amplitude
(K = 3.6 ± 2.4 m s−1). With future Doppler measurements, it will be
possible to measure the planet’s eccentricity and independently test
the assumption we make here that tides damped the eccentricity to
small values.
Transiting exoplanet population comparison Figure 3 compares GJ
1132b to other known transiting exoplanets. Data for this plot were
drawn from the NASA Exoplanet Archive63 on 25 August 2015.
16. a rocky planet transiting a nearby low-mass star 16
Egregious errors in the catalogue were replaced with appropriate
literature values. In the mass-radius panel, individual planets are
shaded with a white-to-black greyscale that is inversely proportional
σM/Mp
2
+ σR/Rp
2
, where σM and σR are the uncertainties on the
planet mass, Mp, and radius, Rp. Planets with precise measurements
are dark, and those with large mass or radius uncertainties are light.
In the distance-radius panel, some planets did not have distances
listed in the Exoplanet Archive. For those systems, we calculated ap-
proximate distances from the J-band magnitudes, estimated stellar
radii, effective temperatures, and a table of bolometric corrections44
(interpolating in Teff to estimate BCJ).
Code availability Analyses were conducted primarily in Python.
Although not cleanly packaged for general use, for the sake of trans-
parency we make the custom code used for transit and radial velocity
fitting available at http://github.com/zkbt/transit. It relies on
three freely available packages: eb (http://github.com/mdwarfgeek/
eb), emcee (http://github.com/dfm/emcee), and George (http://
github.com/dfm/george). Code used to generate the exoplanet popu-
lation comparison is available at http://github.com/zkbt/exopop.
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