The document summarizes the discovery of six transiting exoplanets orbiting the star Kepler-11. Photometry from the Kepler spacecraft revealed periodic dips in the star's brightness consistent with multiple transiting planets. Six planetary candidates were identified, with orbital periods ranging from 10 to 47 days for the inner five planets. Radial velocity measurements confirmed the planetary nature of the five inner planets and allowed for mass estimates. The outermost sixth planet was also validated as a planet. Analysis of the transit times, durations and depths provided insights into the properties, dynamics, and stability of this unique six-planet system.
1) The document reports the discovery of two new circumbinary planets, Kepler-34b and Kepler-35b, orbiting binary star systems.
2) Kepler-34b orbits two sun-like stars every 289 days, while Kepler-35b orbits a pair of smaller stars every 131 days.
3) Analysis of photometric and spectroscopic data confirms the planetary nature of the transiting bodies and determines system parameters like the planets' masses and radii.
This document summarizes the discovery of two Earth-sized planets orbiting the star Kepler-20. Precise photometric data from the Kepler spacecraft revealed periodic transit signals indicating planets with sizes of 1.03 times (Kepler-20 e) and 0.87 times (Kepler-20 f) Earth's radius orbiting the star. Statistical analysis shows the planetary interpretation of the transit signals is over three orders of magnitude more likely than alternative hypotheses. The planets are likely rocky in composition.
This document summarizes the discovery of two new circumbinary planets, Kepler-34b and Kepler-35b, found using data from the Kepler spacecraft. Kepler-34b orbits two sun-like stars every 289 days, while Kepler-35b orbits a pair of smaller stars every 131 days. Both planets are gas giants that experience large variations in stellar radiation from the orbital motion of their parent stars. Analysis of Kepler photometry and spectroscopic data determined the orbital and physical parameters of the planets and their host star systems. The discovery of these planets implies that over 1% of close binary star systems have giant planets in aligned orbits, representing millions of planets in the Milky Way galaxy.
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.
A super earth transiting a naked-eye starSérgio Sacani
This document summarizes the detection of transits of an exoplanet orbiting the star 55 Cnc, using photometry from the MOST space telescope. The transits match the period, phase, duration, and depth predicted for the innermost planet of 55 Cnc, designated 55 Cnc e. Analysis of the transit data indicates the planet has a mass of 8.57 Earth masses, a radius of 1.63 Earth radii, and a dense composition of rock and iron. This makes 55 Cnc e similar to other dense super-Earth exoplanets in short orbits, unlike lower-density super-Earths further from their stars. The brightness of 55 Cnc will enable further study of this transiting exoplanet system.
This document summarizes the discovery of Kepler-413b, a Neptune-sized circumbinary planet orbiting the eclipsing binary star system Kepler-413. The planet has an orbital period of approximately 66 days and an eccentric orbit with a semimajor axis of 0.355 AU. Analysis of the Kepler light curve revealed the planet's orbit is misaligned with the binary star plane by about 2.5 degrees, causing it to sometimes fail to transit one of the stars. The orbital configuration of the system places the planet interior to the habitable zone but its obliquity may undergo fluctuations on precession timescales.
This document summarizes the discovery of a transiting circumbinary planet (PH1) in a quadruple star system by volunteers with the Planet Hunters citizen science project. PH1 orbits outside a 20-day eclipsing binary consisting of an F dwarf and an M dwarf star. It has a radius of 6.18 ± 0.17 R⊕ and an upper mass limit of 169 M⊕. Beyond PH1's orbit is a distant visual binary bound to the system, making this the first known case of a transiting planet in a quadruple star configuration. Planet Hunters volunteers identified transit features in the Kepler light curve of KIC 4862625 through visual inspection and discussion, leading to the confirmation and characterization
The kepler 10_planetary_system_revisited_by_harpsSérgio Sacani
This document discusses observations of the Kepler-10 planetary system made with the HARPS-N spectrograph. The observations resulted in improved precision for the masses of Kepler-10b and Kepler-10c. Kepler-10b's mass was determined to be 3.33 ± 0.49 Earth masses, confirming its rocky composition. Kepler-10c's mass of 17.2 ± 1.9 Earth masses makes it the first strong evidence of a class of more massive solid Neptune-sized planets with longer orbital periods. The improved mass measurements will help constrain models of the internal structure and composition of these planets.
1) The document reports the discovery of two new circumbinary planets, Kepler-34b and Kepler-35b, orbiting binary star systems.
2) Kepler-34b orbits two sun-like stars every 289 days, while Kepler-35b orbits a pair of smaller stars every 131 days.
3) Analysis of photometric and spectroscopic data confirms the planetary nature of the transiting bodies and determines system parameters like the planets' masses and radii.
This document summarizes the discovery of two Earth-sized planets orbiting the star Kepler-20. Precise photometric data from the Kepler spacecraft revealed periodic transit signals indicating planets with sizes of 1.03 times (Kepler-20 e) and 0.87 times (Kepler-20 f) Earth's radius orbiting the star. Statistical analysis shows the planetary interpretation of the transit signals is over three orders of magnitude more likely than alternative hypotheses. The planets are likely rocky in composition.
This document summarizes the discovery of two new circumbinary planets, Kepler-34b and Kepler-35b, found using data from the Kepler spacecraft. Kepler-34b orbits two sun-like stars every 289 days, while Kepler-35b orbits a pair of smaller stars every 131 days. Both planets are gas giants that experience large variations in stellar radiation from the orbital motion of their parent stars. Analysis of Kepler photometry and spectroscopic data determined the orbital and physical parameters of the planets and their host star systems. The discovery of these planets implies that over 1% of close binary star systems have giant planets in aligned orbits, representing millions of planets in the Milky Way galaxy.
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.
A super earth transiting a naked-eye starSérgio Sacani
This document summarizes the detection of transits of an exoplanet orbiting the star 55 Cnc, using photometry from the MOST space telescope. The transits match the period, phase, duration, and depth predicted for the innermost planet of 55 Cnc, designated 55 Cnc e. Analysis of the transit data indicates the planet has a mass of 8.57 Earth masses, a radius of 1.63 Earth radii, and a dense composition of rock and iron. This makes 55 Cnc e similar to other dense super-Earth exoplanets in short orbits, unlike lower-density super-Earths further from their stars. The brightness of 55 Cnc will enable further study of this transiting exoplanet system.
This document summarizes the discovery of Kepler-413b, a Neptune-sized circumbinary planet orbiting the eclipsing binary star system Kepler-413. The planet has an orbital period of approximately 66 days and an eccentric orbit with a semimajor axis of 0.355 AU. Analysis of the Kepler light curve revealed the planet's orbit is misaligned with the binary star plane by about 2.5 degrees, causing it to sometimes fail to transit one of the stars. The orbital configuration of the system places the planet interior to the habitable zone but its obliquity may undergo fluctuations on precession timescales.
This document summarizes the discovery of a transiting circumbinary planet (PH1) in a quadruple star system by volunteers with the Planet Hunters citizen science project. PH1 orbits outside a 20-day eclipsing binary consisting of an F dwarf and an M dwarf star. It has a radius of 6.18 ± 0.17 R⊕ and an upper mass limit of 169 M⊕. Beyond PH1's orbit is a distant visual binary bound to the system, making this the first known case of a transiting planet in a quadruple star configuration. Planet Hunters volunteers identified transit features in the Kepler light curve of KIC 4862625 through visual inspection and discussion, leading to the confirmation and characterization
The kepler 10_planetary_system_revisited_by_harpsSérgio Sacani
This document discusses observations of the Kepler-10 planetary system made with the HARPS-N spectrograph. The observations resulted in improved precision for the masses of Kepler-10b and Kepler-10c. Kepler-10b's mass was determined to be 3.33 ± 0.49 Earth masses, confirming its rocky composition. Kepler-10c's mass of 17.2 ± 1.9 Earth masses makes it the first strong evidence of a class of more massive solid Neptune-sized planets with longer orbital periods. The improved mass measurements will help constrain models of the internal structure and composition of these planets.
An earth sized_planet_in_the_habitable_zone_of_a_cool_starSérgio Sacani
This document describes the discovery of Kepler-186f, an Earth-sized planet orbiting within the habitable zone of its host star Kepler-186, a cool M-dwarf star. Kepler-186f receives a similar amount of stellar radiation as Earth and models suggest it could harbor liquid water on its surface if it has an Earth-like atmosphere. At 1.11 times the size of Earth, Kepler-186f is the smallest planet discovered to date within the habitable zone of its star. The five planets orbiting Kepler-186, including Kepler-186f, likely formed from the protoplanetary disk around the star and provide the first Earth-sized candidate for a habitable world.
A super earth_sized_planet_orbiting_in_or_near_the_habitable_zone_around_sun_...Sérgio Sacani
This document summarizes the discovery of a super-Earth-sized planet orbiting in or near the habitable zone of a Sun-like star called Kepler-69. Using data from the Kepler spacecraft, astronomers detected two planets transiting Kepler-69, called Kepler-69b and Kepler-69c. Kepler-69c is estimated to have a radius of 1.7 Earth radii and orbit every 242.5 days, placing it close to the star's habitable zone where liquid water could exist on the surface. At 1.7 Earth radii, Kepler-69c represents the smallest planet found by Kepler to be potentially habitable, and is an important discovery on the path to finding the first true Earth analog.
Radial velocity monitoring has found the signature of a Msin i = 1:3 M planet located within the Habitable Zone of Proxima
Centauri, the Sun’s closest neighbor (Anglada-Escudé et al. 2016). Despite a hotter past and an active host star the planet Proxima b
could have retained enough volatiles to sustain surface habitability (Ribas et al. 2016). Here we use a 3D Global Climate Model (GCM)
to simulate Proxima b’s atmosphere and water cycle for its two likely rotation modes (the 1:1 and 3:2 spin-orbit resonances) while
varying the unconstrained surface water inventory and atmospheric greenhouse eect (represented here with a CO2-N2 atmosphere.)
We find that a broad range of atmospheric compositions can allow surface liquid water. On a tidally-locked planet with a surface water
inventory larger than 0.6 Earth ocean, liquid water is always present (assuming 1 bar of N2), at least in the substellar region. Liquid
water covers the whole planet for CO2 partial pressures & 1 bar. For smaller water inventories, water can be trapped on the night side,
forming either glaciers or lakes, depending on the amount of greenhouse gases. With a non-synchronous rotation, a minimum CO2
pressure of 10 mbar (assuming 1 bar of N2) is required to avoid falling into a completely frozen snowball state if water is abundant.
If the planet is dryer, 0.5 bar of CO2 would suce to prevent the trapping of any arbitrary small water inventory into polar ice
caps. More generally, any low-obliquity planet within the classical habitable zone of its star should be in one of the climate regimes
discussed here.
We use our GCM to produce reflection/emission spectra and phase curves for the dierent rotations and surface volatile inventories.
We find that atmospheric characterization will be possible by direct imaging with forthcoming large telescopes thanks to an angular
separation of 7=D at 1 m (with the E-ELT) and a contrast of 10 7. The magnitude of the planet will allow for high-resolution
spectroscopy and the search for molecular signatures, including H2O, O2, and CO2.
The observation of thermal phase curves, although challenging, can be attempted with JWST, thanks to a contrast of 210 5 at 10 m.
Proxima b will also be an exceptional target for future IR interferometers. Within a decade it will be possible to image Proxima b and
possibly determine whether this exoplanet’s surface is habitable.
A vast thin_plane_of_corotating_dwarf_galaxies_orbiting_the_andromeda_galaxySérgio Sacani
1. A study using data from the Pan-Andromeda Archaeological Survey finds that approximately half of the dwarf galaxy satellites orbiting the Andromeda galaxy are confined to a highly planar structure that is at least 400 kiloparsecs in diameter but only 14.1 kiloparsecs thick.
2. Radial velocity measurements reveal that 13 of the 15 dwarf galaxies within this structure share the same sense of rotation around Andromeda.
3. The existence of this thin, co-rotating planar structure of dwarf galaxies provides strong evidence that a significant fraction of satellite galaxies can have coherent orbital and angular momentum properties within their host galaxy.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
The document summarizes observations of two giant radio lobes emanating from the center of the Milky Way galaxy. The lobes extend about 60 degrees from the galactic center and correspond closely with previously observed gamma-ray "Fermi bubbles". The lobes contain three ridge-like substructures that curve towards the galactic west as they extend away from the center. Strong magnetic fields of up to 15 microgauss permeate the lobes. The observations indicate that the radio lobes originate from a biconical outflow driven by intense star formation in the galactic center, rather than activity from the supermassive black hole, and have transported a huge amount of magnetic energy into the galactic halo over at least the past 10 million years.
Lenz et al. discovered that soft particles at the nano- and microscale can form "clumpy crystals" where particles partially overlap and form regular lattices of clumps. This challenges ideas that soft materials will behave similarly to atomic and molecular systems. The discovery provides another example of how soft materials display unconventional behavior. An analysis of the satellites orbiting Andromeda found that about half are rotating coherently in a thin planar structure, providing a new constraint on galaxy formation theories. Further evidence suggests organized planar distributions of satellites may be common for nearby galaxy groups. The findings compound issues with the number of predicted versus observed satellites and suggest the structures themselves are not ancient.
DISCOVERY OF A GALAXY CLUSTER WITH A VIOLENTLY STARBURSTING CORE AT z = 2:506Sérgio Sacani
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray
emission at zspec = 2:506, which contains 11 massive (M & 1011M) galaxies in the central 80kpc
region (11.6 overdensity). We have spectroscopically conrmed 17 member galaxies with 11 from CO
and the remaining ones from H. The X-ray luminosity, stellar mass content and velocity dispersion
all point to a collapsed, cluster-sized dark matter halo with mass M200c = 1013:90:2M, making it
the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this
structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive
galaxies classied as quiescent. The star formation rate (SFR) in the 80kpc core reaches 3400 M
yr 1 with a gas depletion time of 200 Myr, suggesting that we caught this cluster in rapid build-up
of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst
fraction ( 25%, compared to 3%-5% in the eld). The presence of both a collapsed, cluster-sized
halo and a predominant population of massive SFGs suggests that this structure could represent an
important transition phase between protoclusters and mature clusters. It provides evidence that the
main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster,
providing new insights into massive cluster formation at early epochs. The large integrated stellar
mass at such high redshift challenges our understanding of massive cluster formation.
Kepler-1647b is the largest and longest-period Kepler transiting circumbinary planet discovered to date. It orbits an eclipsing binary star system with an orbital period of approximately 1100 days, making it one of the longest-period transiting planets known. The planet is around 1.06 times the size of Jupiter and perturbes the times of the stellar eclipses, allowing its mass to be measured at 1.52 times that of Jupiter. Despite its long orbital period compared to Earth, the planet resides in the habitable zone of the binary star system throughout its orbit. The discovery of this unusual planetary system provides insights into theories of planet formation and dynamics in multiple star systems.
The document summarizes observations of periodic increases in luminosity from a young protostar, L54361, arising from variable accretion rates. Key points:
- L54361's luminosity varies periodically every 25.34 days, increasing by a factor of 10 in about a week as material is accreted from a circumbinary disk onto the central protostar.
- This periodic pulsed accretion is attributed to the gravitational influence of an unseen binary companion perturbing the circumbinary disk.
- Follow-up observations found spatially resolved scattered light structures that vary with the same period, supporting the interpretation of variable illumination from pulsed accretion.
This document summarizes the discovery of three new planets that orbit two stars rather than a single star. Key points:
- Three planets have been discovered orbiting binary star systems using the Kepler space telescope. This confirms that circumbinary planets are common, not rare occurrences.
- Analysis estimates that at least 1% of close binary star systems have circumbinary planets, meaning there are millions distributed throughout the Milky Way.
- While these three planets are too hot or cold to support life, circumbinary planets could exist in habitable zones, though none have been found yet in such zones.
- Kepler will continue observations and may find circumbinary planets in longer orbits that could be habitable in the future.
An interacting binary_system_powers_precessing_outflows_of_an_evolved_starSérgio Sacani
1) The authors discovered that the central star system in the planetary nebula Fleming 1 is a binary system with an orbital period of 1.1953 days.
2) They determine that the binary likely consists of a white dwarf primary star with a mass of 0.56-0.7 solar masses and a hotter white dwarf secondary star with a temperature over 120,000 K that provides the ionizing photons to power the nebula.
3) The discovery confirms that binary interactions can explain the precessing outflows and point-symmetric structures seen in Fleming 1 and other planetary nebulae with similar features.
Three new circumbinary planets have been discovered orbiting binary star systems, rather than single stars. This establishes a new class of planets and shows that circumbinary planets are not rare, with an estimated frequency of at least 1% for short-period binary systems, implying millions exist in the Milky Way. While the three discovered planets are too hot or cold to support life, circumbinary planets could potentially be habitable.
A giant planet around a metal poor star of extragalactic originSérgio Sacani
This document reports the detection of a giant planet orbiting the metal-poor star HIP 13044, which belongs to a group of stars accreted from a disrupted satellite galaxy. Radial velocity observations revealed periodic variations indicating a planetary companion with a minimum mass of 1.25 Jupiter masses and an orbital period of 16.2 days. Further analysis ruled out stellar activity as the cause, confirming the planetary origin of the radial velocity signal. As HIP 13044 likely originated from an extragalactic system, this planet may be the first discovered planet of extragalactic origin.
We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using
a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts
of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution
than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in
the northern periphery, with no comparable counterparts in the South. We compare these data to
detailed simulations of the LMC disk outskirts, following interactions with its low mass companion,
the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field.
The simulations are used to assess the origin of the northern structures, including also the low density
stellar arc recently identified in the DES data by Mackey et al. (2015) at ∼ 15 degrees. We conclude
that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar
structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to
constrain the LMC’s interaction history with and impact parameter of the SMC. More generally, we
find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for
1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion
around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are
driven by dwarf-dwarf interactions.
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.
Beyond the Kuiper Belt Edge: New High Perihelion Trans-Neptunian Objects With...Sérgio Sacani
We are conducting a survey for distant solar system objects beyond the Kuiper
Belt edge ( 50 AU) with new wide-field cameras on the Subaru and CTIO tele-
scopes. We are interested in the orbits of objects that are decoupled from the
giant planet region in order to understand the structure of the outer solar sys-
tem, including whether a massive planet exists beyond a few hundred AU as first
reported in Trujillo and Sheppard (2014). In addition to discovering extreme
trans-Neptunian objects detailed elsewhere, we have found several objects with
high perihelia (q > 40 AU) that differ from the extreme and inner Oort cloud
objects due to their moderate semi-major axes (50 < a < 100 AU) and eccen-
tricities (e . 0.3). Newly discovered objects 2014 FZ71 and 2015 FJ345 have
the third and fourth highest perihelia known after Sedna and 2012 VP113, yet
their orbits are not nearly as eccentric or distant. We found several of these high
perihelion but moderate orbit objects and observe that they are mostly near Nep-
tune mean motion resonances and have significant inclinations (i > 20 degrees).
These moderate objects likely obtained their unusual orbits through combined
interactions with Neptune’s mean motion resonances and the Kozai resonance,
similar to the origin scenarios for 2004 XR190. We also find the distant 2008
ST291 has likely been modified by the MMR+KR mechanism through the 6:1
Neptune resonance. We discuss these moderately eccentric, distant objects along
with some other interesting low inclination outer classical belt objects like 2012
FH84 discovered in our ongoing survey.
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.
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.
Uma equipe formada por astrônomos de Israel, da Europa, da Coreia e dos EUA, anunciou a descoberta de um exoplaneta gigante gasoso circumbinário, na zona habitável de seu par de estrelas, uma ocorrência surpreendentemente comum para os exoplanetas circumbinários descobertos pela missão Kepler/K2 da NASA.
Lembrando o planeta da ficção, Tatooine, exoplanetas circumbinários orbitam duas estrelas e assim têm dois sóis em seu céu.
O exoplaneta circumbinário, recém-descoberto, denominado de Kepler-453b, leva 240.5 dias para orbitar suas estrelas, enquanto as estrelas orbitam uma com relação a outra a cada 27.3 dias.
A estrela maior, a Kepler-453A, é similar ao nosso Sol, contendo 94% da massa do Sol, enquanto que a estrela menor, a Kepler-453B, tem cerca de 20% da massa e é mais fria e mais apagada.
O sistema binário, localiza-se na constelação de Lyra, e está a aproximadamente 1400 anos-luz de distância da Terra. Estima-se que esse sistema tenha entre 1 e 2 bilhões de anos de vida, sendo bem mais novo que o nosso Sistema Solar.
Também conhecido como KIC 9632895b, o Kepler-453b tem um raio 6.2 vezes maior que o da Terra. Sua massa não foi medida nos dados atuais, mas provavelmente ele deve ter cerca de 16 vezes a massa da Terra.
De acordo com os astrônomos, o Kepler-453b, é o terceiro planeta circumbinário da missão Kepler, descoberto na zona habitável de um par de estrelas.
Devido ao seu tamanho, e a sua natureza gasosa, o planeta pouco provavelmente deve abrigar a vida como nós a conhecemos. Contudo, ele pode, como os gigantes gasosos do Sistema Solar, ter grandes luas, e essas luas poderiam ser habitáveis. Sua órbita se manterá estável por 10 milhões de anos, aumentando a possibilidade da vida se formar nas suas luas.
Com o número de exoplanetas circumbinários conhecidos agora em dez, os cientistas podem começar a comparar diferentes sistemas e procurar uma tendência. Os sistemas tendem a ser bem compactos e podem aparecer num grande número de configurações.
Uma vez pensados como sendo raros e até mesmo impossíveis de existir, essa e outras descobertas do Kepler, confirmam que esses planetas são comuns na nossa Via Láctea.
“A diversidade e complexidade desses sistemas circumbinários é algo maravilhoso. Cada novo planeta circumbinário, é uma joia, revelando algo inesperado e desafiador”, disse o Prof. William Welsh da Universidade Estadual de San Diego, e o primeiro autor do artigo que descreve a descoberta, publicado no Astrophysical Journal.
Fonte:
http://www.sci-news.com/astronomy/science-kepler453b-circumbinary-exoplanet-03117.html
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
An earth sized_planet_in_the_habitable_zone_of_a_cool_starSérgio Sacani
This document describes the discovery of Kepler-186f, an Earth-sized planet orbiting within the habitable zone of its host star Kepler-186, a cool M-dwarf star. Kepler-186f receives a similar amount of stellar radiation as Earth and models suggest it could harbor liquid water on its surface if it has an Earth-like atmosphere. At 1.11 times the size of Earth, Kepler-186f is the smallest planet discovered to date within the habitable zone of its star. The five planets orbiting Kepler-186, including Kepler-186f, likely formed from the protoplanetary disk around the star and provide the first Earth-sized candidate for a habitable world.
A super earth_sized_planet_orbiting_in_or_near_the_habitable_zone_around_sun_...Sérgio Sacani
This document summarizes the discovery of a super-Earth-sized planet orbiting in or near the habitable zone of a Sun-like star called Kepler-69. Using data from the Kepler spacecraft, astronomers detected two planets transiting Kepler-69, called Kepler-69b and Kepler-69c. Kepler-69c is estimated to have a radius of 1.7 Earth radii and orbit every 242.5 days, placing it close to the star's habitable zone where liquid water could exist on the surface. At 1.7 Earth radii, Kepler-69c represents the smallest planet found by Kepler to be potentially habitable, and is an important discovery on the path to finding the first true Earth analog.
Radial velocity monitoring has found the signature of a Msin i = 1:3 M planet located within the Habitable Zone of Proxima
Centauri, the Sun’s closest neighbor (Anglada-Escudé et al. 2016). Despite a hotter past and an active host star the planet Proxima b
could have retained enough volatiles to sustain surface habitability (Ribas et al. 2016). Here we use a 3D Global Climate Model (GCM)
to simulate Proxima b’s atmosphere and water cycle for its two likely rotation modes (the 1:1 and 3:2 spin-orbit resonances) while
varying the unconstrained surface water inventory and atmospheric greenhouse eect (represented here with a CO2-N2 atmosphere.)
We find that a broad range of atmospheric compositions can allow surface liquid water. On a tidally-locked planet with a surface water
inventory larger than 0.6 Earth ocean, liquid water is always present (assuming 1 bar of N2), at least in the substellar region. Liquid
water covers the whole planet for CO2 partial pressures & 1 bar. For smaller water inventories, water can be trapped on the night side,
forming either glaciers or lakes, depending on the amount of greenhouse gases. With a non-synchronous rotation, a minimum CO2
pressure of 10 mbar (assuming 1 bar of N2) is required to avoid falling into a completely frozen snowball state if water is abundant.
If the planet is dryer, 0.5 bar of CO2 would suce to prevent the trapping of any arbitrary small water inventory into polar ice
caps. More generally, any low-obliquity planet within the classical habitable zone of its star should be in one of the climate regimes
discussed here.
We use our GCM to produce reflection/emission spectra and phase curves for the dierent rotations and surface volatile inventories.
We find that atmospheric characterization will be possible by direct imaging with forthcoming large telescopes thanks to an angular
separation of 7=D at 1 m (with the E-ELT) and a contrast of 10 7. The magnitude of the planet will allow for high-resolution
spectroscopy and the search for molecular signatures, including H2O, O2, and CO2.
The observation of thermal phase curves, although challenging, can be attempted with JWST, thanks to a contrast of 210 5 at 10 m.
Proxima b will also be an exceptional target for future IR interferometers. Within a decade it will be possible to image Proxima b and
possibly determine whether this exoplanet’s surface is habitable.
A vast thin_plane_of_corotating_dwarf_galaxies_orbiting_the_andromeda_galaxySérgio Sacani
1. A study using data from the Pan-Andromeda Archaeological Survey finds that approximately half of the dwarf galaxy satellites orbiting the Andromeda galaxy are confined to a highly planar structure that is at least 400 kiloparsecs in diameter but only 14.1 kiloparsecs thick.
2. Radial velocity measurements reveal that 13 of the 15 dwarf galaxies within this structure share the same sense of rotation around Andromeda.
3. The existence of this thin, co-rotating planar structure of dwarf galaxies provides strong evidence that a significant fraction of satellite galaxies can have coherent orbital and angular momentum properties within their host galaxy.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
The document summarizes observations of two giant radio lobes emanating from the center of the Milky Way galaxy. The lobes extend about 60 degrees from the galactic center and correspond closely with previously observed gamma-ray "Fermi bubbles". The lobes contain three ridge-like substructures that curve towards the galactic west as they extend away from the center. Strong magnetic fields of up to 15 microgauss permeate the lobes. The observations indicate that the radio lobes originate from a biconical outflow driven by intense star formation in the galactic center, rather than activity from the supermassive black hole, and have transported a huge amount of magnetic energy into the galactic halo over at least the past 10 million years.
Lenz et al. discovered that soft particles at the nano- and microscale can form "clumpy crystals" where particles partially overlap and form regular lattices of clumps. This challenges ideas that soft materials will behave similarly to atomic and molecular systems. The discovery provides another example of how soft materials display unconventional behavior. An analysis of the satellites orbiting Andromeda found that about half are rotating coherently in a thin planar structure, providing a new constraint on galaxy formation theories. Further evidence suggests organized planar distributions of satellites may be common for nearby galaxy groups. The findings compound issues with the number of predicted versus observed satellites and suggest the structures themselves are not ancient.
DISCOVERY OF A GALAXY CLUSTER WITH A VIOLENTLY STARBURSTING CORE AT z = 2:506Sérgio Sacani
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray
emission at zspec = 2:506, which contains 11 massive (M & 1011M) galaxies in the central 80kpc
region (11.6 overdensity). We have spectroscopically conrmed 17 member galaxies with 11 from CO
and the remaining ones from H. The X-ray luminosity, stellar mass content and velocity dispersion
all point to a collapsed, cluster-sized dark matter halo with mass M200c = 1013:90:2M, making it
the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this
structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive
galaxies classied as quiescent. The star formation rate (SFR) in the 80kpc core reaches 3400 M
yr 1 with a gas depletion time of 200 Myr, suggesting that we caught this cluster in rapid build-up
of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst
fraction ( 25%, compared to 3%-5% in the eld). The presence of both a collapsed, cluster-sized
halo and a predominant population of massive SFGs suggests that this structure could represent an
important transition phase between protoclusters and mature clusters. It provides evidence that the
main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster,
providing new insights into massive cluster formation at early epochs. The large integrated stellar
mass at such high redshift challenges our understanding of massive cluster formation.
Kepler-1647b is the largest and longest-period Kepler transiting circumbinary planet discovered to date. It orbits an eclipsing binary star system with an orbital period of approximately 1100 days, making it one of the longest-period transiting planets known. The planet is around 1.06 times the size of Jupiter and perturbes the times of the stellar eclipses, allowing its mass to be measured at 1.52 times that of Jupiter. Despite its long orbital period compared to Earth, the planet resides in the habitable zone of the binary star system throughout its orbit. The discovery of this unusual planetary system provides insights into theories of planet formation and dynamics in multiple star systems.
The document summarizes observations of periodic increases in luminosity from a young protostar, L54361, arising from variable accretion rates. Key points:
- L54361's luminosity varies periodically every 25.34 days, increasing by a factor of 10 in about a week as material is accreted from a circumbinary disk onto the central protostar.
- This periodic pulsed accretion is attributed to the gravitational influence of an unseen binary companion perturbing the circumbinary disk.
- Follow-up observations found spatially resolved scattered light structures that vary with the same period, supporting the interpretation of variable illumination from pulsed accretion.
This document summarizes the discovery of three new planets that orbit two stars rather than a single star. Key points:
- Three planets have been discovered orbiting binary star systems using the Kepler space telescope. This confirms that circumbinary planets are common, not rare occurrences.
- Analysis estimates that at least 1% of close binary star systems have circumbinary planets, meaning there are millions distributed throughout the Milky Way.
- While these three planets are too hot or cold to support life, circumbinary planets could exist in habitable zones, though none have been found yet in such zones.
- Kepler will continue observations and may find circumbinary planets in longer orbits that could be habitable in the future.
An interacting binary_system_powers_precessing_outflows_of_an_evolved_starSérgio Sacani
1) The authors discovered that the central star system in the planetary nebula Fleming 1 is a binary system with an orbital period of 1.1953 days.
2) They determine that the binary likely consists of a white dwarf primary star with a mass of 0.56-0.7 solar masses and a hotter white dwarf secondary star with a temperature over 120,000 K that provides the ionizing photons to power the nebula.
3) The discovery confirms that binary interactions can explain the precessing outflows and point-symmetric structures seen in Fleming 1 and other planetary nebulae with similar features.
Three new circumbinary planets have been discovered orbiting binary star systems, rather than single stars. This establishes a new class of planets and shows that circumbinary planets are not rare, with an estimated frequency of at least 1% for short-period binary systems, implying millions exist in the Milky Way. While the three discovered planets are too hot or cold to support life, circumbinary planets could potentially be habitable.
A giant planet around a metal poor star of extragalactic originSérgio Sacani
This document reports the detection of a giant planet orbiting the metal-poor star HIP 13044, which belongs to a group of stars accreted from a disrupted satellite galaxy. Radial velocity observations revealed periodic variations indicating a planetary companion with a minimum mass of 1.25 Jupiter masses and an orbital period of 16.2 days. Further analysis ruled out stellar activity as the cause, confirming the planetary origin of the radial velocity signal. As HIP 13044 likely originated from an extragalactic system, this planet may be the first discovered planet of extragalactic origin.
We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using
a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts
of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution
than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in
the northern periphery, with no comparable counterparts in the South. We compare these data to
detailed simulations of the LMC disk outskirts, following interactions with its low mass companion,
the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field.
The simulations are used to assess the origin of the northern structures, including also the low density
stellar arc recently identified in the DES data by Mackey et al. (2015) at ∼ 15 degrees. We conclude
that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar
structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to
constrain the LMC’s interaction history with and impact parameter of the SMC. More generally, we
find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for
1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion
around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are
driven by dwarf-dwarf interactions.
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.
Beyond the Kuiper Belt Edge: New High Perihelion Trans-Neptunian Objects With...Sérgio Sacani
We are conducting a survey for distant solar system objects beyond the Kuiper
Belt edge ( 50 AU) with new wide-field cameras on the Subaru and CTIO tele-
scopes. We are interested in the orbits of objects that are decoupled from the
giant planet region in order to understand the structure of the outer solar sys-
tem, including whether a massive planet exists beyond a few hundred AU as first
reported in Trujillo and Sheppard (2014). In addition to discovering extreme
trans-Neptunian objects detailed elsewhere, we have found several objects with
high perihelia (q > 40 AU) that differ from the extreme and inner Oort cloud
objects due to their moderate semi-major axes (50 < a < 100 AU) and eccen-
tricities (e . 0.3). Newly discovered objects 2014 FZ71 and 2015 FJ345 have
the third and fourth highest perihelia known after Sedna and 2012 VP113, yet
their orbits are not nearly as eccentric or distant. We found several of these high
perihelion but moderate orbit objects and observe that they are mostly near Nep-
tune mean motion resonances and have significant inclinations (i > 20 degrees).
These moderate objects likely obtained their unusual orbits through combined
interactions with Neptune’s mean motion resonances and the Kozai resonance,
similar to the origin scenarios for 2004 XR190. We also find the distant 2008
ST291 has likely been modified by the MMR+KR mechanism through the 6:1
Neptune resonance. We discuss these moderately eccentric, distant objects along
with some other interesting low inclination outer classical belt objects like 2012
FH84 discovered in our ongoing survey.
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.
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.
Uma equipe formada por astrônomos de Israel, da Europa, da Coreia e dos EUA, anunciou a descoberta de um exoplaneta gigante gasoso circumbinário, na zona habitável de seu par de estrelas, uma ocorrência surpreendentemente comum para os exoplanetas circumbinários descobertos pela missão Kepler/K2 da NASA.
Lembrando o planeta da ficção, Tatooine, exoplanetas circumbinários orbitam duas estrelas e assim têm dois sóis em seu céu.
O exoplaneta circumbinário, recém-descoberto, denominado de Kepler-453b, leva 240.5 dias para orbitar suas estrelas, enquanto as estrelas orbitam uma com relação a outra a cada 27.3 dias.
A estrela maior, a Kepler-453A, é similar ao nosso Sol, contendo 94% da massa do Sol, enquanto que a estrela menor, a Kepler-453B, tem cerca de 20% da massa e é mais fria e mais apagada.
O sistema binário, localiza-se na constelação de Lyra, e está a aproximadamente 1400 anos-luz de distância da Terra. Estima-se que esse sistema tenha entre 1 e 2 bilhões de anos de vida, sendo bem mais novo que o nosso Sistema Solar.
Também conhecido como KIC 9632895b, o Kepler-453b tem um raio 6.2 vezes maior que o da Terra. Sua massa não foi medida nos dados atuais, mas provavelmente ele deve ter cerca de 16 vezes a massa da Terra.
De acordo com os astrônomos, o Kepler-453b, é o terceiro planeta circumbinário da missão Kepler, descoberto na zona habitável de um par de estrelas.
Devido ao seu tamanho, e a sua natureza gasosa, o planeta pouco provavelmente deve abrigar a vida como nós a conhecemos. Contudo, ele pode, como os gigantes gasosos do Sistema Solar, ter grandes luas, e essas luas poderiam ser habitáveis. Sua órbita se manterá estável por 10 milhões de anos, aumentando a possibilidade da vida se formar nas suas luas.
Com o número de exoplanetas circumbinários conhecidos agora em dez, os cientistas podem começar a comparar diferentes sistemas e procurar uma tendência. Os sistemas tendem a ser bem compactos e podem aparecer num grande número de configurações.
Uma vez pensados como sendo raros e até mesmo impossíveis de existir, essa e outras descobertas do Kepler, confirmam que esses planetas são comuns na nossa Via Láctea.
“A diversidade e complexidade desses sistemas circumbinários é algo maravilhoso. Cada novo planeta circumbinário, é uma joia, revelando algo inesperado e desafiador”, disse o Prof. William Welsh da Universidade Estadual de San Diego, e o primeiro autor do artigo que descreve a descoberta, publicado no Astrophysical Journal.
Fonte:
http://www.sci-news.com/astronomy/science-kepler453b-circumbinary-exoplanet-03117.html
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
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.
The document summarizes research on the Kepler-9 planetary system. It finds that Kepler-9b and Kepler-9c are Saturn-sized planets with orbital periods of 19.24 and 39.08 days, respectively. Kepler-9d is a super-Earth with a period of 1.59 days. The Kepler-9 system was the first discovered using the transit method to have transit time variations (TTVs) detected for its planets. The research uses transit and radial velocity data to determine various properties of the three planets, including radius, orbital period, TTV, semi-major axis, mass, and density. It finds the first multi-planetary system where TTVs were detected, adding scientific value.
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
Eccentricity from transit_photometry_small_planets_in_kepler_multi_planet_sys...Sérgio Sacani
Artigo descreve estudo que mostra que a órbita dos exoplanetas terrestres são na sua maioria órbitas circulares, o que é bom para se procurar por vida e o que vem causando uma revolução no entendimento sobre os sistemas de exoplanteas.
Know the star_know_the_planet_discovery_of_l_ate_type_companions_to_two_exopl...Sérgio Sacani
This document summarizes the discovery of additional late-type stellar companions to two exoplanet host stars, HD 2638 and 30 Ari B, using adaptive optics imaging. For both systems, the companions were found to share common proper motion with the primaries, indicating they are physically associated. The estimated orbital periods of the new companions are 130 years for HD 2638 and 80 years for 30 Ari B. This makes 30 Ari B the second confirmed quadruple star system known to host an exoplanet. The discoveries provide additional examples of how binary companions can influence exoplanet dynamics and formation.
The stellar orbit distribution in present-day galaxies inferred from the CALI...Sérgio Sacani
Galaxy formation entails the hierarchical assembly of mass,
along with the condensation of baryons and the ensuing, selfregulating
star formation1,2
. The stars form a collisionless system
whose orbit distribution retains dynamical memory that
can constrain a galaxy’s formation history3
. The orbits dominated
by ordered rotation, with near-maximum circularity
λz≈ 1, are called kinematically cold, and the orbits dominated
by random motion, with low circularity λz≈ 0, are kinematically
hot. The fraction of stars on ‘cold’ orbits, compared with
the fraction on ‘hot’ orbits, speaks directly to the quiescence
or violence of the galaxies’ formation histories4,5
. Here we
present such orbit distributions, derived from stellar kinematic
maps through orbit-based modelling for a well-defined,
large sample of 300 nearby galaxies. The sample, drawn from
the CALIFA survey6, includes the main morphological galaxy
types and spans a total stellar mass range from 108.7 to 1011.9
solar masses. Our analysis derives the orbit-circularity distribution
as a function of galaxy mass and its volume-averaged
total distribution. We find that across most of the considered
mass range and across morphological types, there are more
stars on ‘warm’ orbits defined as 0.25 ≤λz≤ 0.8 than on either
‘cold’ or ‘hot’ orbits. This orbit-based ‘Hubble diagram’ provides
a benchmark for galaxy formation simulations in a cosmological
context.
This pilot survey used modest aperture telescopes to image 8 nearby spiral galaxies in order to search for stellar tidal streams. Ultra-deep imaging revealed 6 previously undetected extensive (up to 30 kpc) stellar structures likely from tidally disrupted satellites. A diversity of tidal feature morphologies was found, including great circle-like streams, remote shells, and jets emerging from disks. Simulations predict tidal debris should be common and match the observed variety, providing evidence minor mergers have shaped disk galaxies since z=1.
Telescópio Espacial Kepler descobre primeiro exoplaneta do tamanho da Terra n...GOASA
This document describes the discovery of Kepler-186f, an Earth-sized planet orbiting within the habitable zone of its host star Kepler-186, a cool M-dwarf star. Kepler-186f receives a similar amount of stellar radiation as Earth and models suggest it could harbor liquid water on its surface if it has an Earth-like atmosphere. At 1.11 times the size of Earth, it is the smallest planet discovered to date within the habitable zone of its star. The five planets orbiting Kepler-186, including Kepler-186f, likely formed from the protoplanetary disk around the star and may have migrated inward over time. Kepler-186f's orbit places it in a region where
1) Small planets between Earth and Neptune in size are much more common than large Jupiter-sized planets, especially those with orbits within 1 AU of their host stars.
2) Doppler and transit surveys have revealed thousands of exoplanets and characterized their masses, sizes, orbital properties, and host star characteristics.
3) These observations support the core accretion model of planet formation and show that while our solar system is one outcome, there is great diversity in planetary systems with characteristics not seen locally.
Transit timing observations from kepler i. statistical analysis of the first...Sérgio Sacani
This document analyzes transit timing observations from the first four months of Kepler mission data. It finds that at least 12% (~65) of planet candidates show evidence of transit timing variations (TTVs), suggesting non-Keplerian motion likely due to gravitational interactions with other planets. While longer observation time is needed, TTVs could confirm multiple planet systems identified by Kepler and provide insights into planetary system dynamics and planet formation. The analysis measures individual transit times, assesses the significance of any variations compared to linear and quadratic ephemeris models, and identifies planet candidates warranting further TTV study.
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.
Is there an_exoplanet_in_the_solar_systemSérgio Sacani
We investigate the prospects for the capture of the proposed Planet 9 from other
stars in the Sun’s birth cluster. Any capture scenario must satisfy three conditions:
the encounter must be more distant than ∼ 150 au to avoid perturbing the Kuiper
belt; the other star must have a wide-orbit planet (a & 100 au); the planet must be
captured onto an appropriate orbit to sculpt the orbital distribution of wide-orbit
Solar System bodies. Here we use N-body simulations to show that these criteria may
be simultaneously satisfied. In a few percent of slow close encounters in a cluster,
bodies are captured onto heliocentric, Planet 9-like orbits. During the ∼ 100 Myr
cluster phase, many stars are likely to host planets on highly-eccentric orbits with
apastron distances beyond 100 au if Neptune-sized planets are common and susceptible
to planet–planet scattering. While the existence of Planet 9 remains unproven, we
consider capture from one of the Sun’s young brethren a plausible route to explain such
an object’s orbit. Capture appears to predict a large population of Trans-Neptunian
Objects (TNOs) whose orbits are aligned with the captured planet, and we propose
that different formation mechanisms will be distinguishable based on their imprint on
the distribution of TNOs
We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster
galaxies, with r-band monochromatic luminosity Lr = 8 14L (4:3 7:5 1044 erg s 1). These
super spiral galaxies are also giant and massive, with diameter D = 57 134 kpc and stellar mass
Mstars = 0:3 3:4 1011M. We nd 53 super spirals out of a complete sample of 1616 SDSS
galaxies with redshift z < 0:3 and Lr > 8L. The closest example is found at z = 0:089. We use
existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS
and WISE colors are consistent with normal star-forming spirals on the blue sequence. However, the
extreme masses and rapid SFRs of 5 65M yr 1 place super spirals in a sparsely populated region
of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a
diverse range of environments, from isolation to cluster centers. We nd four super spiral galaxy
systems that are late-stage major mergers{a possible clue to their formation. We suggest that super
spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become
massive lenticular galaxies after they are cut o from their gas supply and their disks fade.
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.
A dusty star-forming galaxy at z = 6 revealed by strong gravitational lensingSérgio Sacani
Since their discovery, submillimetre-selected galaxies1,2
have revolutionized the field of galaxy formation and evolution.
From the hundreds of square degrees mapped at submillimetre
wavelengths3–5
, only a handful of sources have
been confirmed to lie at z> 5 (refs 6–10) and only two at z ≥ 6
(refs 11,12). All of these submillimetre galaxies are rare examples
of extreme starburst galaxies with star formation rates
of ≳1,000 M⊙ yr−1
and therefore are not representative
of the general population of dusty star-forming galaxies.
Consequently, our understanding of the nature of these
sources, at the earliest epochs, is still incomplete. Here, we
report the spectroscopic identification of a gravitationally
amplified (μ= 9.3 ± 1.0) dusty star-forming galaxy at z= 6.027.
After correcting for gravitational lensing, we derive an intrinsic
less-extreme star formation rate of 380 ± 50 M⊙ yr−1
for this source and find that its gas and dust properties are
similar to those measured for local ultra luminous infrared
galaxies, extending the local trends to a poorly explored territory
in the early Universe. The star-formation efficiency
of this galaxy is similar to those measured in its local analogues13,
despite a ~12 Gyr difference in cosmic time.
Architecture and dynamics of kepler's candidate multiple transiting planet sy...Sérgio Sacani
This document summarizes the architecture and dynamics of Kepler's candidate multiple transiting planet systems. It finds:
1) Virtually all systems are dynamically stable based on numerical integration assuming a mass-radius relationship.
2) The distribution of observed period ratios is clustered just outside resonances, particularly the 2:1 resonance.
3) These characteristics suggest the majority of multi-candidate systems are true planetary systems, not false positives.
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.
Similar to A closely packed system of low mass, low-density planets transiting kepler-11 (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.