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 observations of the debris disk around the subgiant star κ CrB using Herschel and Keck. Herschel spatially resolved images of the debris disk, the first such images of a disk around a subgiant star. Keck radial velocity monitoring provided evidence for a second planetary companion around κ CrB. Keck adaptive optics imaging placed an upper limit on the mass of this companion. Modeling of the Herschel images showed the dust is broadly distributed but could not distinguish between a single wide belt or two narrow belts. The observations are consistent with dynamical depletion or collisional erosion clearing the inner regions of the disk.
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.
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.
Small dust particles escaping from Pluto's moons Nix and Hydra could temporarily form a ring around Pluto due to impacts, but the solar radiation pressure would remove about half of 1 micrometer particles within a year by causing collisions with Pluto and its moons. Numerical simulations found that a tenuous ring with an optical depth of 6×10^-11 could be maintained by dust released from Nix and Hydra.
A closely packed system of low mass, low-density planets transiting kepler-11Sérgio Sacani
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.
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.
The fornax deep_survey_with_vst_i_the_extended_and_diffuse_stellar_halo_of_ng...Sérgio Sacani
We have started a new deep, multi-imaging survey of the Fornax cluster, dubbed Fornax Deep
Survey (FDS), at the VLT Survey Telescope. In this paper we present the deep photometry inside
two square degrees around the bright galaxy NGC 1399 in the core of the cluster. We found that
the core of the Fornax cluster is characterised by a very extended and diffuse envelope surrounding
the luminous galaxy NGC 1399: we map the surface brightness out to 33 arcmin (∼ 192 kpc)
from the galaxy center and down to μg ∼ 31 mag arcsec−2 in the g band. The deep photometry
allows us to detect a faint stellar bridge in the intracluster region on the west side of NGC 1399
and towards NGC 1387. By analyzing the integrated colors of this feature, we argue that it
could be due to the ongoing interaction between the two galaxies, where the outer envelope of
NGC 1387 on its east side is stripped away. By fitting the light profile, we found that exists a
physical break radius in the total light distribution at R = 10 arcmin (∼ 58 kpc) that sets the
transition region between the bright central galaxy and the outer exponential halo, and that the
stellar halo contributes for 60% of the total light of the galaxy (Sec. 3.5). We discuss the main
implications of this work on the build-up of the stellar halo at the center of the Fornax cluster.
By comparing with the numerical simulations of the stellar halo formation for the most massive
BCGs (i.e. 13 < logM200/M⊙ < 14), we find that the observed stellar halo mass fraction is
consistent with a halo formed through the multiple accretion of progenitors with stellar mass in
the range 108 − 1011 M⊙. This might suggest that the halo of NGC 1399 has also gone through
a major merging event. The absence of a significant number of luminous stellar streams and
tidal tails out to 192 kpc suggests that the epoch of this strong interaction goes back to an early
formation epoch. Therefore, differently from the Virgo cluster, the extended stellar halo around
NGC 1399 is characterised by a more diffuse and well-mixed component, including the ICL.
Stellar-like objects with effective temperatures of 2700K and below are referred to as
20 "ultracool dwarfs"1. This heterogeneous group includes both extremely low-mass stars
21 and brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion),
22 and represents about 15% of the stellar-like objects in the vicinity of the Sun2. Based on
23 the small masses and sizes of their protoplanetary disks3,4, core-accretion theory for
24 ultracool dwarfs predicts a large, but heretofore undetected, population of close-in
25 terrestrial planets5, ranging from metal-rich Mercury-sized planets6 to more hospitable
26 volatile-rich Earth-sized planets7. Here we report the discovery of three short-period
27 Earth-sized planets transiting an ultracool dwarf star 12 parsecs away. The inner two
28 planets receive four and two times the irradiation of Earth, respectively, placing them
29 close to the inner edge of the habitable zone of the star8. Eleven orbits remain possible
30 for the third planet based on our data, the most likely resulting in an irradiation
31 significantly smaller than Earth's. The infrared brightness of the host star combined
32 with its Jupiter-like size offer the possibility of constraining the composition and
33 thoroughly characterizing the atmospheric properties of the components of this nearby
34 planetary system, notably to detect potential biosignatures.
This document summarizes observations of the debris disk around the subgiant star κ CrB using Herschel and Keck. Herschel spatially resolved images of the debris disk, the first such images of a disk around a subgiant star. Keck radial velocity monitoring provided evidence for a second planetary companion around κ CrB. Keck adaptive optics imaging placed an upper limit on the mass of this companion. Modeling of the Herschel images showed the dust is broadly distributed but could not distinguish between a single wide belt or two narrow belts. The observations are consistent with dynamical depletion or collisional erosion clearing the inner regions of the disk.
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.
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.
Small dust particles escaping from Pluto's moons Nix and Hydra could temporarily form a ring around Pluto due to impacts, but the solar radiation pressure would remove about half of 1 micrometer particles within a year by causing collisions with Pluto and its moons. Numerical simulations found that a tenuous ring with an optical depth of 6×10^-11 could be maintained by dust released from Nix and Hydra.
A closely packed system of low mass, low-density planets transiting kepler-11Sérgio Sacani
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.
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.
The fornax deep_survey_with_vst_i_the_extended_and_diffuse_stellar_halo_of_ng...Sérgio Sacani
We have started a new deep, multi-imaging survey of the Fornax cluster, dubbed Fornax Deep
Survey (FDS), at the VLT Survey Telescope. In this paper we present the deep photometry inside
two square degrees around the bright galaxy NGC 1399 in the core of the cluster. We found that
the core of the Fornax cluster is characterised by a very extended and diffuse envelope surrounding
the luminous galaxy NGC 1399: we map the surface brightness out to 33 arcmin (∼ 192 kpc)
from the galaxy center and down to μg ∼ 31 mag arcsec−2 in the g band. The deep photometry
allows us to detect a faint stellar bridge in the intracluster region on the west side of NGC 1399
and towards NGC 1387. By analyzing the integrated colors of this feature, we argue that it
could be due to the ongoing interaction between the two galaxies, where the outer envelope of
NGC 1387 on its east side is stripped away. By fitting the light profile, we found that exists a
physical break radius in the total light distribution at R = 10 arcmin (∼ 58 kpc) that sets the
transition region between the bright central galaxy and the outer exponential halo, and that the
stellar halo contributes for 60% of the total light of the galaxy (Sec. 3.5). We discuss the main
implications of this work on the build-up of the stellar halo at the center of the Fornax cluster.
By comparing with the numerical simulations of the stellar halo formation for the most massive
BCGs (i.e. 13 < logM200/M⊙ < 14), we find that the observed stellar halo mass fraction is
consistent with a halo formed through the multiple accretion of progenitors with stellar mass in
the range 108 − 1011 M⊙. This might suggest that the halo of NGC 1399 has also gone through
a major merging event. The absence of a significant number of luminous stellar streams and
tidal tails out to 192 kpc suggests that the epoch of this strong interaction goes back to an early
formation epoch. Therefore, differently from the Virgo cluster, the extended stellar halo around
NGC 1399 is characterised by a more diffuse and well-mixed component, including the ICL.
Stellar-like objects with effective temperatures of 2700K and below are referred to as
20 "ultracool dwarfs"1. This heterogeneous group includes both extremely low-mass stars
21 and brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion),
22 and represents about 15% of the stellar-like objects in the vicinity of the Sun2. Based on
23 the small masses and sizes of their protoplanetary disks3,4, core-accretion theory for
24 ultracool dwarfs predicts a large, but heretofore undetected, population of close-in
25 terrestrial planets5, ranging from metal-rich Mercury-sized planets6 to more hospitable
26 volatile-rich Earth-sized planets7. Here we report the discovery of three short-period
27 Earth-sized planets transiting an ultracool dwarf star 12 parsecs away. The inner two
28 planets receive four and two times the irradiation of Earth, respectively, placing them
29 close to the inner edge of the habitable zone of the star8. Eleven orbits remain possible
30 for the third planet based on our data, the most likely resulting in an irradiation
31 significantly smaller than Earth's. The infrared brightness of the host star combined
32 with its Jupiter-like size offer the possibility of constraining the composition and
33 thoroughly characterizing the atmospheric properties of the components of this nearby
34 planetary system, notably to detect potential biosignatures.
The habitability of Proxima Centauri b - I. Irradiation, rotation and volatil...Sérgio Sacani
Proxima b is a planet with a minimum mass of 1.3 M⊕ orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass,
active star and the Sun’s closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b
and its ability to maintain liquid water on its surface. We set the stage by estimating the current high-energy irradiance of the planet
and show that the planet currently receives 30 times more EUV radiation than Earth and 250 times more X-rays. We compute the time
evolution of the star’s spectrum, which is essential for modeling the flux received over Proxima b’s lifetime. We also show that Proxima
b’s obliquity is likely null and its spin is either synchronous or in a 3:2 spin-orbit resonance, depending on the planet’s eccentricity and
level of triaxiality. Next we consider the evolution of Proxima b’s water inventory. We use our spectral energy distribution to compute
the hydrogen loss from the planet with an improved energy-limited escape formalism. Despite the high level of stellar activity we find
that Proxima b is likely to have lost less than an Earth ocean’s worth of hydrogen (EOH) before it reached the HZ 100–200 Myr after
its formation. The largest uncertainty in our work is the initial water budget, which is not constrained by planet formation models. We
conclude that Proxima b is a viable candidate habitable planet.
Analysis of most_light_curves_of_five_young_stars_in_taurus_auriga_and_lupus_3...Sérgio Sacani
This document analyzes light curves from the MOST satellite of five young stars in star-forming regions. Light curves of three spotted weak-line T Tauri stars (V410 Tau, V987 Tau, and Lupus 3-14) show small values of the solar-type differential rotation parameter, indicating slightly non-rigid rotation. Light curves of another spotted weak-line T Tauri star (Lupus 3-48) are consistent with rigid rotation. Three similar flares were detected in the light curve of Lupus 3-14. The light curve of the classical T Tauri star RY Tau showed continuous decreasing brightness over three weeks of observation with variable modulation and no obvious periodic signal.
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.
Extensive Noachian fluvial systems in Arabia Terra: Implications for early Ma...Sérgio Sacani
Valley networks are some of the strongest lines of evidence for
extensive fluvial activity on early (Noachian; >3.7 Ga) Mars. However,
their purported absence on certain ancient terrains, such as
Arabia Terra, is at variance with patterns of precipitation as predicted
by “warm and wet” climate models. This disagreement has contributed
to the development of an alternative “icy highlands” scenario,
whereby valley networks were formed by the melting of highland ice
sheets. Here, we show through regional mapping that Arabia Terra
shows evidence for extensive networks of sinuous ridges. We interpret
these ridge features as inverted fluvial channels that formed in
the Noachian, before being subject to burial and exhumation. The
inverted channels developed on extensive aggrading flood plains. As
the inverted channels are both sourced in, and traverse across, Arabia
Terra, their formation is inconsistent with discrete, localized sources
of water, such as meltwater from highland ice sheets. Our results are
instead more consistent with an early Mars that supported widespread
precipitation and runoff.
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 analyzes data from the open star cluster M11 to determine its fundamental properties. Photometry of stars in M11 was performed using images taken through two filters with a telescope. A color-magnitude diagram was created and fit with theoretical models, revealing M11 to be around 250 million years old, located 5930 light years away, and having a similar iron-to-hydrogen ratio as the sun. Analysis of independent star clusters provides insights into patterns of galaxy formation and evolution.
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.
1) The document reports the discovery of the first known Trojan asteroid of Earth, 2010 TK7.
2) 2010 TK7 was discovered in infrared data from the WISE spacecraft. Follow-up optical observations confirmed it is trapped in a stable orbit around the L4 Lagrangian point ahead of Earth.
3) The asteroid's orbit is stable over at least 10,000 years, though its position becomes chaotic beyond 250 years in the past or future due to gravitational interactions.
1) The document hypothesizes that dark matter images were accidentally recorded by cameras on the TSS-1R satellite during a 1996 NASA mission mishap. Disk-like images seen moving beyond the receding satellite are proposed to be evidence of dark matter.
2) It further conjectures that these disk images each represent two single-notch 2D disks "stuck together" from a lower plane of existence, representing doubled magnetic monopoles on that plane.
3) A mathematical formula is proposed to describe the number of fundamental particles ("koilon quanta") that make up electrons and other fundamental particles on different planes of existence.
Predictions of the_atmospheric_composition_of_gj_1132_bSérgio Sacani
GJ 1132 b is a nearby Earth-sized exoplanet transiting an M dwarf, and is amongst the most highly
characterizable small exoplanets currently known. In this paper we study the interaction of a magma
ocean with a water-rich atmosphere on GJ 1132b and determine that it must have begun with more
than 5 wt% initial water in order to still retain a water-based atmosphere. We also determine the
amount of O2
that can build up in the atmosphere as a result of hydrogen dissociation and loss.
We find that the magma ocean absorbs at most ∼ 10% of the O2 produced, whereas more than
90% is lost to space through hydrodynamic drag. The most common outcome for GJ 1132 b from our
simulations is a tenuous atmosphere dominated by O2
, although for very large initial water abundances
atmospheres with several thousands of bars of O2
are possible. A substantial steam envelope would
indicate either the existence of an earlier H2
envelope or low XUV flux over the system’s lifetime. A
steam atmosphere would also imply the continued existence of a magma ocean on GJ 1132 b. Further
modeling is needed to study the evolution of CO2
or N2
-rich atmospheres on GJ 1132 b.
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 nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
The puzzling source_in_ngc6388_a_possible_planetary_tidal_disruption_eventSérgio Sacani
Artigo descreve a descoberta da destruição de um planeta ao passar próximo a uma estrela do tipo anã branca presente dentro do aglomerado globular de estrelas NGC 6388. Para isso os astrônomos utilizaram um arsenal de telescópios.
This document summarizes star forming regions in the constellation of Cepheus. It describes several giant molecular cloud complexes located at various distances from the Sun, ranging from clouds within 500 pc to regions associated with the Perseus spiral arm at 2-3 kpc. Key regions discussed include the Cepheus Flare clouds below 500 pc, three OB associations (Cep OB2, Cep OB3, Cep OB4) located 600-900 pc away, and the well-known high mass star forming region S 140 located at 900 pc. Tables list molecular clouds and young stars identified in the Cepheus region. Maps show the distribution of clouds, extinction, and pre-main sequence stars across Cepheus.
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.
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.
Rapid formation of large dust grains in the luminous supernova SN 2010jlGOASA
This document summarizes observations of rapid dust formation in the luminous supernova SN 2010jl over multiple epochs from 26 to 868 days past peak brightness. Analysis of emission line profiles shows increasing extinction over time, indicating continuous dust formation. The extinction curve implies the presence of very large (>1 micron) dust grains. Thermal emission models suggest dust temperatures declining from 2300K to 1100K over time, requiring carbonaceous rather than silicate dust. Combined extinction and emission data indicate a dust mass of ~0.0025 solar masses at 868 days, growing rapidly and expected to reach ~0.5 solar masses by 8000 days if production continues. The results provide evidence for very efficient and rapid dust formation in the dense
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.
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 nustar extragalactic_survey_a_first_sensitive_lookSérgio Sacani
The document summarizes the first ten sources detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) as part of its extragalactic survey. NuSTAR provides the first sensitive census of the cosmic X-ray background source population at energies above 10 keV. The ten sources have a broad range of redshifts and luminosities, with a median redshift of 0.7 and luminosity of 3×10^44 erg/s. Based on broad-band spectroscopy and SED analysis, the dominant population is quasars with luminosities above 10^44 erg/s, of which around 50% are obscured. However, none are Compton thick and the fraction of Compton thick quasars is constrained to
Persistence of black holes through a cosmological bounceSérgio Sacani
The document discusses whether black holes could persist through a cosmological bounce, where the universe recollapses and then bounces into a new expansion phase. It finds that there is a mass range where black holes could form during the big crunch ("BCBHs") without merging with pre-existing black holes ("PCBHs"). This mass range depends on factors like the density at bounce and whether extra dimensions exist. Observational signatures could distinguish black holes forming just before or after the bounce. The persistence of black holes relates to issues in cyclic cosmology models and scenarios where the universe evolves to maximize black hole formation.
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 habitability of Proxima Centauri b - I. Irradiation, rotation and volatil...Sérgio Sacani
Proxima b is a planet with a minimum mass of 1.3 M⊕ orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass,
active star and the Sun’s closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b
and its ability to maintain liquid water on its surface. We set the stage by estimating the current high-energy irradiance of the planet
and show that the planet currently receives 30 times more EUV radiation than Earth and 250 times more X-rays. We compute the time
evolution of the star’s spectrum, which is essential for modeling the flux received over Proxima b’s lifetime. We also show that Proxima
b’s obliquity is likely null and its spin is either synchronous or in a 3:2 spin-orbit resonance, depending on the planet’s eccentricity and
level of triaxiality. Next we consider the evolution of Proxima b’s water inventory. We use our spectral energy distribution to compute
the hydrogen loss from the planet with an improved energy-limited escape formalism. Despite the high level of stellar activity we find
that Proxima b is likely to have lost less than an Earth ocean’s worth of hydrogen (EOH) before it reached the HZ 100–200 Myr after
its formation. The largest uncertainty in our work is the initial water budget, which is not constrained by planet formation models. We
conclude that Proxima b is a viable candidate habitable planet.
Analysis of most_light_curves_of_five_young_stars_in_taurus_auriga_and_lupus_3...Sérgio Sacani
This document analyzes light curves from the MOST satellite of five young stars in star-forming regions. Light curves of three spotted weak-line T Tauri stars (V410 Tau, V987 Tau, and Lupus 3-14) show small values of the solar-type differential rotation parameter, indicating slightly non-rigid rotation. Light curves of another spotted weak-line T Tauri star (Lupus 3-48) are consistent with rigid rotation. Three similar flares were detected in the light curve of Lupus 3-14. The light curve of the classical T Tauri star RY Tau showed continuous decreasing brightness over three weeks of observation with variable modulation and no obvious periodic signal.
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.
Extensive Noachian fluvial systems in Arabia Terra: Implications for early Ma...Sérgio Sacani
Valley networks are some of the strongest lines of evidence for
extensive fluvial activity on early (Noachian; >3.7 Ga) Mars. However,
their purported absence on certain ancient terrains, such as
Arabia Terra, is at variance with patterns of precipitation as predicted
by “warm and wet” climate models. This disagreement has contributed
to the development of an alternative “icy highlands” scenario,
whereby valley networks were formed by the melting of highland ice
sheets. Here, we show through regional mapping that Arabia Terra
shows evidence for extensive networks of sinuous ridges. We interpret
these ridge features as inverted fluvial channels that formed in
the Noachian, before being subject to burial and exhumation. The
inverted channels developed on extensive aggrading flood plains. As
the inverted channels are both sourced in, and traverse across, Arabia
Terra, their formation is inconsistent with discrete, localized sources
of water, such as meltwater from highland ice sheets. Our results are
instead more consistent with an early Mars that supported widespread
precipitation and runoff.
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 analyzes data from the open star cluster M11 to determine its fundamental properties. Photometry of stars in M11 was performed using images taken through two filters with a telescope. A color-magnitude diagram was created and fit with theoretical models, revealing M11 to be around 250 million years old, located 5930 light years away, and having a similar iron-to-hydrogen ratio as the sun. Analysis of independent star clusters provides insights into patterns of galaxy formation and evolution.
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.
1) The document reports the discovery of the first known Trojan asteroid of Earth, 2010 TK7.
2) 2010 TK7 was discovered in infrared data from the WISE spacecraft. Follow-up optical observations confirmed it is trapped in a stable orbit around the L4 Lagrangian point ahead of Earth.
3) The asteroid's orbit is stable over at least 10,000 years, though its position becomes chaotic beyond 250 years in the past or future due to gravitational interactions.
1) The document hypothesizes that dark matter images were accidentally recorded by cameras on the TSS-1R satellite during a 1996 NASA mission mishap. Disk-like images seen moving beyond the receding satellite are proposed to be evidence of dark matter.
2) It further conjectures that these disk images each represent two single-notch 2D disks "stuck together" from a lower plane of existence, representing doubled magnetic monopoles on that plane.
3) A mathematical formula is proposed to describe the number of fundamental particles ("koilon quanta") that make up electrons and other fundamental particles on different planes of existence.
Predictions of the_atmospheric_composition_of_gj_1132_bSérgio Sacani
GJ 1132 b is a nearby Earth-sized exoplanet transiting an M dwarf, and is amongst the most highly
characterizable small exoplanets currently known. In this paper we study the interaction of a magma
ocean with a water-rich atmosphere on GJ 1132b and determine that it must have begun with more
than 5 wt% initial water in order to still retain a water-based atmosphere. We also determine the
amount of O2
that can build up in the atmosphere as a result of hydrogen dissociation and loss.
We find that the magma ocean absorbs at most ∼ 10% of the O2 produced, whereas more than
90% is lost to space through hydrodynamic drag. The most common outcome for GJ 1132 b from our
simulations is a tenuous atmosphere dominated by O2
, although for very large initial water abundances
atmospheres with several thousands of bars of O2
are possible. A substantial steam envelope would
indicate either the existence of an earlier H2
envelope or low XUV flux over the system’s lifetime. A
steam atmosphere would also imply the continued existence of a magma ocean on GJ 1132 b. Further
modeling is needed to study the evolution of CO2
or N2
-rich atmospheres on GJ 1132 b.
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 nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
The puzzling source_in_ngc6388_a_possible_planetary_tidal_disruption_eventSérgio Sacani
Artigo descreve a descoberta da destruição de um planeta ao passar próximo a uma estrela do tipo anã branca presente dentro do aglomerado globular de estrelas NGC 6388. Para isso os astrônomos utilizaram um arsenal de telescópios.
This document summarizes star forming regions in the constellation of Cepheus. It describes several giant molecular cloud complexes located at various distances from the Sun, ranging from clouds within 500 pc to regions associated with the Perseus spiral arm at 2-3 kpc. Key regions discussed include the Cepheus Flare clouds below 500 pc, three OB associations (Cep OB2, Cep OB3, Cep OB4) located 600-900 pc away, and the well-known high mass star forming region S 140 located at 900 pc. Tables list molecular clouds and young stars identified in the Cepheus region. Maps show the distribution of clouds, extinction, and pre-main sequence stars across Cepheus.
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.
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.
Rapid formation of large dust grains in the luminous supernova SN 2010jlGOASA
This document summarizes observations of rapid dust formation in the luminous supernova SN 2010jl over multiple epochs from 26 to 868 days past peak brightness. Analysis of emission line profiles shows increasing extinction over time, indicating continuous dust formation. The extinction curve implies the presence of very large (>1 micron) dust grains. Thermal emission models suggest dust temperatures declining from 2300K to 1100K over time, requiring carbonaceous rather than silicate dust. Combined extinction and emission data indicate a dust mass of ~0.0025 solar masses at 868 days, growing rapidly and expected to reach ~0.5 solar masses by 8000 days if production continues. The results provide evidence for very efficient and rapid dust formation in the dense
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.
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 nustar extragalactic_survey_a_first_sensitive_lookSérgio Sacani
The document summarizes the first ten sources detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) as part of its extragalactic survey. NuSTAR provides the first sensitive census of the cosmic X-ray background source population at energies above 10 keV. The ten sources have a broad range of redshifts and luminosities, with a median redshift of 0.7 and luminosity of 3×10^44 erg/s. Based on broad-band spectroscopy and SED analysis, the dominant population is quasars with luminosities above 10^44 erg/s, of which around 50% are obscured. However, none are Compton thick and the fraction of Compton thick quasars is constrained to
Persistence of black holes through a cosmological bounceSérgio Sacani
The document discusses whether black holes could persist through a cosmological bounce, where the universe recollapses and then bounces into a new expansion phase. It finds that there is a mass range where black holes could form during the big crunch ("BCBHs") without merging with pre-existing black holes ("PCBHs"). This mass range depends on factors like the density at bounce and whether extra dimensions exist. Observational signatures could distinguish black holes forming just before or after the bounce. The persistence of black holes relates to issues in cyclic cosmology models and scenarios where the universe evolves to maximize black hole formation.
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.
Black hole growth in the early universe is self regulated and largely hidde...Sérgio Sacani
The study analyzed X-ray data from the Chandra X-ray Observatory to measure black hole growth in galaxies between redshifts 6-8 (0.95-0.7 billion years after the Big Bang). It found:
1) A stacked signal from 197 galaxies at z<6 detected significant X-ray emission, implying black holes grew in tandem with their host galaxies throughout cosmic history.
2) Most vigorously accreting black holes at these early epochs were obscured by significant gas and dust, absorbing most radiation except high-energy X-rays.
3) The obscured black hole growth suggests growth was significantly more than previously thought, but the obscuration prevented contribution to reionizing the Universe.
High pre eruptive water contents preserved in lunar melt inclusionsSérgio Sacani
This study analyzed melt inclusions trapped in olivine crystals from lunar volcanic glass samples. The melt inclusions contained 615-1410 parts per million of water, much higher than previous measurements of lunar samples. They also contained high amounts of fluorine, sulfur, and chlorine similar to primitive terrestrial basalts. This indicates that parts of the lunar interior contain as much water as Earth's upper mantle, challenging theories that the Moon lost its entire volatile inventory during formation. The similarities between the lunar melt inclusions and terrestrial basalts suggest the lunar mantle source was similar in volatile content to Earth's upper mantle.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive function. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
Backreaction of hawking_radiation_on_a_gravitationally_collapsing_star_2_fire...Sérgio Sacani
This document summarizes a numerical study of the backreaction of Hawking radiation on a gravitationally collapsing star. The study finds that including the inward flux of negative energy Hawking radiation in the interior of the star slows its collapse. This causes the star to bounce at a finite radius larger than its horizon, before its core explodes. The full system of Einstein and hydrodynamic equations describing the collapsing star and Hawking radiation flux are solved numerically, as an improvement over previous analytic approximations.
The document reports the detection of a lunar impact flash by two independent observatories on February 11, 2011. Analysis of video footage from both observatories found that a bright flash occurred simultaneously on the lunar rim at 20:36:58 UTC. The estimated selenographic coordinates of the impact site were 88° ± 2° W and 16° ± 1° S. Modeling of the flash characteristics suggests the impactor had a diameter of 6-8 cm and would have created a crater around 4-5 meters in size.
1. VFTS 682 is a very massive star located 29 pc in projection from the young massive cluster R136 in the Tarantula Nebula of the LMC.
2. Spectral modeling finds it has an unusually high luminosity of log(L/L) = 6.5, corresponding to a present-day mass of ~150 solar masses.
3. Its isolation and mass pose the question of whether it formed in situ, which would profoundly impact theories of massive star formation, or if it was ejected from R136, making it the most massive runaway star known.
This document introduces the VLT-FLAMES Tarantula Survey, which obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud. The survey aims to detect massive binary systems through variations in radial velocities and to characterize the properties of O- and B-type stars, addressing questions about stellar and cluster evolution. Spectral classifications are provided for newly discovered emission-line stars, including a new Wolf-Rayet star. The survey data and reduction procedures are overviewed, and upcoming analyses of the massive star properties are announced.
Pawan Kumar Relativistic jets in tidal disruption eventsBaurzhan Alzhanov
- Fast radio bursts (FRBs) are short, intense radio pulses that last about 1 millisecond. One FRB source produced multiple outbursts over several years.
- The leading model is that FRBs originate from young, highly magnetic neutron stars called magnetars. Charged particles are accelerated by magnetic reconnection, producing coherent curvature radiation observed as FRBs.
- FRBs provide insights into neutron star physics and energetic processes in magnetar magnetospheres. Predictions include observing FRB-like bursts at higher frequencies.
A young protoplanet_candidate_embedded_in_the_circumstellar_disk_of_hd100546Sérgio Sacani
This document summarizes observations of HD100546 using high-contrast imaging techniques. A faint emission source was detected near the star at a projected separation of about 47 AU. The position of the source coincides with a deficit in polarization observed from the circumstellar disk. This suggests a physical link between the source and the disk. Considering various scenarios, the authors favor interpreting the source as a young protoplanet currently forming within the disk. Follow-up observations could distinguish between different possible explanations for the observed features. If confirmed, it would be a unique opportunity to study giant planet formation within an optically thick disk.
Kinematics and simulations_of_the_stellar_stream_in_the_halo_of_the_umbrella_...Sérgio Sacani
This document summarizes a study of the stellar stream and substructures around the Umbrella Galaxy (NGC 4651). Deep imaging and spectroscopy were used to characterize the properties and kinematics of the stream. Tracer objects like globular clusters and planetary nebulae were identified and found to delineate a kinematically cold feature in position-velocity space. Dynamical modeling suggests the stream originated from the tidal disruption of a dwarf galaxy on a highly eccentric orbit about 6-10 billion years ago. This work demonstrates the feasibility of using discrete tracers to recover the kinematics and model the dynamics of low surface brightness stellar streams around distant galaxies.
Sdss1133 an unsually_perssitent_transient_in_a_nearby_dwarf_galaxySérgio Sacani
This document summarizes observations of SDSS1133, an unusual transient object offset from the center of a nearby dwarf galaxy. SDSS1133 has been detected in observations spanning 63 years, and exhibits broad emission lines and strong variability. While initially classified as a supernova due to its non-detection in 2005, more recent observations over the past decade show it has rebrightened over a magnitude and displays properties consistent with both an active galactic nucleus and luminous blue variable star eruptions. Its nature remains ambiguous between an extreme example of pre-supernova mass loss or a potential candidate for a recoiling supermassive black hole.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
This document summarizes the results of a 180 ks Chandra-LETGS observation of Mrk 509 as part of a larger multi-wavelength campaign. The observation detected several absorption features in the X-ray spectrum originating from an ionized absorber, including ions with three distinct ionization degrees. The lowest ionized component is slightly redshifted and not in pressure equilibrium with the others, likely belonging to the host galaxy's interstellar medium. The other two components are outflowing at velocities of around -200 and -455 km/s. Simultaneous HST-COS observations detected 13 UV kinematic components, and at least three can be associated with the X-ray components, providing evidence that the UV and X-
1) The Fermi bubbles are giant gamma-ray emitting structures extending above and below the galactic center.
2) The bubbles may have been formed by periodic capture of stars by the supermassive black hole at the galactic center, releasing energy of around 3x10^52 ergs per capture.
3) This energy injection could produce very hot plasma, accelerating electrons that produce radio and gamma-ray emission through synchrotron radiation and inverse Compton scattering.
A LUMINOUS Be+WHITE DWARF SUPERSOFT SOURCE IN THE WING OF THE SMC: MAXI J0158...Carlos Bella
This document summarizes a study of the X-ray source MAXI J0158-744, which was detected by the MAXI instrument in November 2011. It exhibited an unusually bright and brief X-ray flare with a luminosity exceeding 10^39 erg/s, approaching ultraluminous X-ray source levels. Follow-up observations with Swift and other instruments over subsequent months found the source had a very soft X-ray spectrum characteristic of a supersoft source. Optical spectra of the counterpart revealed emission and absorption features consistent with a B1/2IIIe spectral type star in the Small Magellanic Cloud. The authors propose MAXI J0158-744 is a luminous supersoft source associated with
Periodic mass extinctions_and_the_planet_x_model_reconsideredSérgio Sacani
The 27 Myr periodicity in the fossil extinction record has been con-
firmed in modern data bases dating back 500 Myr, which is twice the time
interval of the original analysis from thirty years ago. The surprising regularity
of this period has been used to reject the Nemesis model. A second
model based on the sun’s vertical galactic oscillations has been challenged
on the basis of an inconsistency in period and phasing. The third astronomical
model originally proposed to explain the periodicity is the Planet
X model in which the period is associated with the perihelion precession
of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated
to mass extinctions, a trans-Neptunian super-Earth planet has been proposed
to explain the observation that the inner Oort cloud objects Sedna
and 2012VP113 have perihelia that lie near the ecliptic plane. In this
Letter we reconsider the Planet X model in light of the confluence of the
modern palaeontological and outer solar system dynamical evidence.
Key Words: astrobiology - planets and satellites - Kuiper belt:
general - comets: general
This document summarizes the discovery of an Earth-mass planet orbiting the star Alpha Centauri B. The planet, with a minimum mass similar to Earth, has an orbital period of 3.236 days and is located about 0.04 astronomical units from the star. High-precision radial velocity measurements from the HARPS spectrograph revealed the planet's signal, making it the lightest planet detected around a solar-type star. The discovery demonstrates that current techniques can detect potentially habitable super-Earth planets around Sun-like stars and habitable Earth-like planets around cooler stars.
An Earth-mass planet orbiting a Centauri BCarlos Bella
1) Researchers detected an Earth-mass planet orbiting the star Alpha Centauri B.
2) The planet has a minimum mass similar to Earth and orbits its star with a period of 3.236 days, within 0.04 astronomical units.
3) This makes it the lightest planet detected orbiting a Sun-like star and the closest exoplanet to our solar system found to date.
The James Webb Space Telescope is NASA's next flagship mission. Webb will revolutionize astronomy in the infrared like the Hubble Space Telescope has done for the visible portion of the spectrum over the last 22 years. Webb will reveal the story of the formation of the first starts and galaxies, investigate the processes of planet formation, and trace the origins of life.
The closest known_flyby_of_a_star_to_the_solar_systemSérgio Sacani
The closest known flyby of a star to the solar system was a low-mass binary star system called WISE J072003.20-084651.2, also known as "Scholz's star". By integrating the orbits of this 0.15 solar mass binary system and the Sun, astronomers found that it passed within 0.25 parsecs (52,000 AU) of the Sun about 70,000 years ago, within the outer bounds of the Oort Cloud. This is the closest encounter with a star to the solar system that has been well-constrained in distance and velocity. While the flyby likely had a negligible impact on long-period comets from the Oort Cloud, it highlights the possibility
A 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.
An Earth-sized exoplanet with a Mercury-like compositionSérgio Sacani
Earth, Venus, Mars and some extrasolar terrestrial planets1
have a mass and radius that is consistent with a mass fraction
of about 30% metallic core and 70% silicate mantle2
. At the
inner frontier of the Solar System, Mercury has a completely
different composition, with a mass fraction of about 70%
metallic core and 30% silicate mantle3
. Several formation or
evolution scenarios are proposed to explain this metal-rich
composition, such as a giant impact4, mantle evaporation5
or the depletion of silicate at the inner edge of the protoplanetary
disk6. These scenarios are still strongly debated.
Here, we report the discovery of a multiple transiting planetary
system (K2-229) in which the inner planet has a radius
of 1.165 ± 0.066 Earth radii and a mass of 2.59 ± 0.43 Earth
masses. This Earth-sized planet thus has a core-mass fraction
that is compatible with that of Mercury, although it was
expected to be similar to that of Earth based on host-star
chemistry7
. This larger Mercury analogue either formed with
a very peculiar composition or has evolved, for example, by
losing part of its mantle. Further characterization of Mercurylike
exoplanets such as K2-229 b will help to put the detailed
in situ observations of Mercury (with MESSENGER and
BepiColombo8) into the global context of the formation and
evolution of solar and extrasolar terrestrial planets.
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.
Measurement of Jupiter’s asymmetric gravity fieldSérgio Sacani
The gravity harmonics of a fluid, rotating planet can be decomposed
into static components arising from solid-body rotation and dynamic
components arising from flows. In the absence of internal dynamics,
the gravity field is axially and hemispherically symmetric and is
dominated by even zonal gravity harmonics J2n that are approximately
proportional to qn, where q is the ratio between centrifugal
acceleration and gravity at the planet’s equator1
. Any asymmetry in the
gravity field is attributed to differential rotation and deep atmospheric
flows. The odd harmonics, J3, J5, J7, J9 and higher, are a measure of the
depth of the winds in the different zones of the atmosphere2,3
. Here
we report measurements of Jupiter’s gravity harmonics (both even
and odd) through precise Doppler tracking of the Juno spacecraft
in its polar orbit around Jupiter. We find a north–south asymmetry,
which is a signature of atmospheric and interior flows. Analysis of
the harmonics, described in two accompanying papers4,5
, provides
the vertical profile of the winds and precise constraints for the depth
of Jupiter’s dynamical atmosphere.
A Tale of 3 Dwarf Planets: Ices and Organics on Sedna, Gonggong, and Quaoar f...Sérgio Sacani
The dwarf planets Sedna, Gonggong, and Quaoar are interesting in being somewhat smaller than
the methane-rich bodies of the Kuiper Belt (Pluto, Eris, Makemake), yet large enough to be
spherical and to have possibly undergone interior melting and differentiation. They also reside
on very different orbits, making them an ideal suite of bodies for untangling effects of size and
orbit on present day surface composition. We observed Sedna, Gonggong, and Quaoar with the
NIRSpec instrument on the James Webb Space Telescope (JWST). All three bodies were
observed in the low-resolution prism mode at wavelengths spanning 0.7 to 5.2 μm. Quaoar was
additionally observed at 10x higher spectral resolution from 0.97 to 3.16 μm using mediumresolution gratings. Sedna’s spectrum shows a large number of absorption features due to ethane
(C2H6), as well as acetylene (C2H2), ethylene (C2H4), H2O, and possibly minor CO2.
Gonggong’s spectrum also shows several, but fewer and weaker, ethane features, along with
stronger and cleaner H2O features and CO2 complexed with other molecules. Quaoar’s prism
spectrum shows even fewer and weaker ethane features, the deepest and cleanest H2O features, a
feature at 3.2 μm possibly due to HCN, and CO2 ice. The higher-resolution medium grating
spectrum of Quaoar reveals several overtone and combination bands of ethane and methane
(CH4). Spectra of all three objects show steep red spectral slopes and strong, broad absorptions
between 2.7 and 3.6 μm indicative of complex organic molecules. The suite of light
hydrocarbons and complex organic molecules are interpreted as the products of irradiation of
methane. The differences in apparent abundances of irradiation products among these three
similarly-sized bodies are likely due to their distinctive orbits, which lead to different timescales
of methane retention and to different charged particle irradiation environments. In all cases,
however, the continued presence of light hydrocarbons implies a resupply of methane to the
2
surface. We suggest that these three bodies have undergone internal melting and geochemical
evolution similar to the larger dwarf planets and distinct from all smaller KBOs. The feature
identification presented in this paper is the first step of analysis, and additional insight into the
relative abundances and mixing states of materials on these surfaces will come from future
spectral modeling of these data.
Similar to A super earth transiting a naked-eye star (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
Continuum emission from within the plunging region of black hole discs
A super earth transiting a naked-eye star
1. D RAFT VERSION , A PRIL 27, 2011
Preprint typeset using LTEX style emulateapj v. 11/10/09
A
A SUPER-EARTH TRANSITING A NAKED-EYE STAR⋆
J OSHUA N. W INN 1 , JAYMIE M. M ATTHEWS 2 , R EBEKAH I. DAWSON 3 , DANIEL FABRYCKY 4,5 , M ATTHEW J. H OLMAN 3 ,
T HOMAS K ALLINGER 2,6 , R AINER K USCHNIG 6 , D IMITAR S ASSELOV 3 , D IANA D RAGOMIR 5 , DAVID B. G UENTHER 7 ,
A NTHONY F. J. M OFFAT 8 , JASON F. ROWE 9 , S LAVEK RUCINSKI 10 , W ERNER W. W EISS 6
Submitted to ApJ Letters
ABSTRACT
arXiv:1104.5230v1 [astro-ph.EP] 27 Apr 2011
We have detected transits of the innermost planet “e” orbiting 55 Cnc (V = 6.0), based on two weeks of
precise photometric monitoring with the MOST space telescope. The transits of 55 Cnc e occur with the period
(0.74 d) and phase that had been predicted by Dawson & Fabrycky, and with the expected duration and depth for
the crossing of a Sun-like star by a hot super-Earth. Assuming the star’s mass and radius to be 0.96 ± 0.10 M⊙
and 1.10 ± 0.10 R⊙ , the planet’s mass, radius, and mean density are 8.57 ± 0.64 M⊕ , 1.63 ± 0.16 R⊕ , and
10.9 ± 3.1 g cm−3 . The high density suggests the planet has a rock-iron composition as opposed to hydrogen,
water, or other light elements. This makes 55 Cnc e similar to the other transiting super-Earths in tight orbits
around G stars (Kepler-10b and Corot-7b), and unlike the lower-density super-Earths that are less strongly
irradiated (GJ 1214b and Kepler-11d,e,f). The host star of 55 Cnc e is far brighter than that of any other known
transiting planet, which will facilitate further investigations.
Subject headings: planetary systems — planets and satellites: formation, interiors — stars: individual (55 Cnc)
1. INTRODUCTION transit probability, from 13% to 33%. The occurrence of tran-
Precise Doppler observations have revealed five planets or- sits enhances the importance of an exoplanetary system, be-
biting the nearby G8 V star 55 Cnc (Butler et al. 1997, Marcy cause photometric and spectroscopic observations of transits
et al. 2002, McArthur et al. 2004, Wisdom 2005, Fischer et can reveal a wealth of details about the planet’s dimensions,
al. 2008). Only a few other stars are known to host as many atmosphere, and orbit (see, e.g., Winn 2010).
planets: HD 10180 (Lovis et al. 2011), Kepler-11 (Lissauer et Fischer et al. (2008) searched for transits in their 11-year
al. 2011), and the Sun. Among the other reasons why 55 Cnc photometric record, ruling out transits for planets b (P =
has attracted attention are the 3:1 resonance between two of 14.7 d) and c (44.3 d). However, the time coverage was not
its planets (Ji et al. 2003), the existence of an M dwarf com- complete enough to rule out transits for planets f (260 d) and
d (5200 d), and the precision was insufficient to detect transits
panion at a distance of 103 AU (Mugrauer et al. 2006), and the
of the smallest planet e.
unusually low mass and short period of its innermost planet,
designated “e”. Here we present space-based photometry of 55 Cnc reveal-
ing a transit signal with the characteristics predicted by Daw-
McArthur et al. (2004) reported a period and minimum
son & Fabrycky (2010). Section 2 presents the data, and Sec-
mass for 55 Cnc e of 2.808 d and 14.2 M⊕ , respectively.
Those parameters were confirmed by Fischer et al. (2008). tion 3 presents the light curve analysis, yielding estimates for
More recently, Dawson & Fabrycky (2010) argued that the mass, radius, and density of the planet. In Section 4 we
place 55 Cnc e in the context of the small but growing popu-
55 Cnc e had been mischaracterized due to aliasing in the
radial-velocity data, and that the true period and minimum lation of super-Earths with measured masses and radii.
mass are 0.74 d and 8.3 M⊕ . 2. OBSERVATIONS
One implication of the shorter period would be an increased We observed 55 Cnc with MOST (Microvariability & Os-
⋆ Based on data from the MOST satellite, a Canadian Space Agency mis-
cillations of STars), a Canadian microsatellite equipped with
sion, jointly operated by Dynacon Inc., the University of Toronto Institute
a 15 cm telescope and CCD photometer, capable of short-
for Aerospace Studies, and the University of British Columbia, with the cadence, long-duration ultraprecise optical photometry of
assistance of the University of Vienna. bright stars (Walker et al. 2003, Matthews et al. 2004). MOST
1 Department of Physics, and Kavli Institute for Astrophysics and Space
is in a Sun-synchronous polar orbit 820 km above the termi-
Research, Massachusetts Institute of Technology, Cambridge, MA 02139 nator with an orbital period of 101 min. Its custom broadband
2 Department of Physics and Astronomy, University of British
Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
filter covers the visible spectrum (350-700 nm).
3 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cam- We used the Direct Imaging mode, similar to conventional
bridge, MA 02138 ground-based CCD photometry. The observations spanned a
4 Hubble Fellow nearly continuous 14.5-day interval from 2011 February 07-
5 UCO/Lick Observatory, University of California, Santa Cruz, CA
22, with four interruptions when fine pointing was lost due to
95064 satellite subsystem crashes. Individual exposures lasted 0.5 s
6 University of Vienna, Institute for Astronomy, Türkenschanzstrasse
17, A-1180 Vienna, Austria but were downloaded in “stacks” of either 40 or 80. The me-
7 Department of Astronomy and Physics, Saint Mary’s University, Hal- dian time sampling in the resulting time series is 43 s, outside
ifax, NS B3H 3C3, Canada of the interruptions.
8 Départment de Physique, Université de Montréal, C.P. 6128, Succ.
Centre-Ville, Montréal, QC H3C 3J7, Canada
Data reduction was performed with the method of Rowe et
9 NASA Ames Research Center, Moffett Field, CA 94035 al. (2006), which combines classical aperture photometry and
10 Department of Astronomy & Astrophysics, University of Toronto, 50
point-spread function fitting to the Direct Imaging subraster of
St. George Street, Toronto, ON M5S 3H4, Canada the Science CCD. There are familiar periodic artifacts in the
2. 2 Winn et al. 2011
Transit of b
Relative flux 1.002
1.001
1.000
0.999
0.998 Transits of e
0.997
0 2 4 6 8 10 12 14
Time [HJD − 2,455,600]
1.0004
1.0002
Relative flux
1.0000
0.9998
0.9996
−0.4 −0.2 0.0 0.2 0.4
Phase
F IG . 1.— MOST photometry of 55 Cnc. Upper.—The time series. To reduce the file size, a random subset of 10% of the data points are plotted. Large symbols
represent 0.25 d averages. Vertical bars mark the 20 predicted transit times of planet e, and the single predicted transit of planet b (which was missed when MOST
temporarily lost fine pointing). Lower.—Phased light curve (after removing the 0.079 c d−1 trend), folded with P = 0.736540 d and Tc [HJD] = 2, 453, 094.6924
(Dawson & Fabrycky 2010) and averaged into 2 min phase bins (44 data points per bin). The solid curve is the best-fitting transit model.
time series due to scattered Earthshine, appearing at the or- data were phased with the predicted ephemeris, with no free
bital frequency of the satellite (14.26 c d−1 ) and its lower har- parameters. Nevertheless, when a period search is performed,
monics, as well as sidelobes arising from the amplitude mod- the strongest signal is at 0.74 d and there is no signal at the
ulation of the stray light by the Earth’s rotation. Before the alternative period of 2.82 d. This is demonstrated in Fig-
transit analysis described below, the artifacts were removed ure 2, which shows a Box-fitting Least Squares periodogram
by “prewhitening”: subtracting the best-fitting sinusoids cor- (Kovács et al. 2002). Another measure of the statistical sig-
responding to the strongest satellite harmonics and sidelobes. nificance of the detection is given in Section 3.
This produces minimal effects on the transit signal because The signal has the predicted period, and the observed epoch
the satellite frequency is an order of magnitude higher than the is bracketed by the two predicted epochs of Dawson & Fab-
planet orbital frequency. Indeed the transits were detectable rycky (2010): it is 35 min later than the circular-orbit pre-
even before prewhitening, despite the increased scatter in the diction and 67 min earlier than the eccentric-orbit prediction.
phased light curve. Furthermore the depth and duration of the signal conform
The prewhitened time series is plotted in the upper panel with predictions (see Section 3). With close matches to four
of Figure 1. Variation by a few parts in 10−4 is seen on the predicted parameters (period, phase, depth and duration) we
relatively long timescale of ∼10 d, which could be a mani- consider the existence of transits to be established.
festation of stellar activity and rotation. Fischer et al. (2008)
measured a rotation period of 42.7 ± 2.5 d, which we can- 3. ANALYSIS
not address given the 14.5 d span of our data. For the transit A transit model was fitted to the light curve based on the for-
analysis, the slow variation was filtered out by removing a mulas of Mandel & Agol (2002) and the Monte Carlo Markov
sinusoid with period 12.6 d. Chain (MCMC) code of Holman et al. (2006) and Winn et
The lower panel of Figure 1 shows the data after folding al. (2007). The limb-darkening law was taken to be quadratic
with the Dawson & Fabrycky (2010) ephemeris. A signif- with coefficients u1 = 0.657 and u2 = 0.115, based on a Ku-
icant dip is observed at nearly zero phase, where the tran- rucz model for a star with Teff = 5327 K and log g = 4.48
sit signal would be expected. We emphasize that the signal (Takeda et al. 2007), integrated over the MOST bandpass.
shown in Figure 1 is not the outcome of a period search. The The adjustable parameters were the planet-to-star radius ratio
3. Transits of 55 Cnc e 3
been measured, along with theoretical curves taken from Sea-
7•10−5 ger et al. (2007) for “mathematicians’ planets” composed of
P = 2.81703 d 0.73654 d pure hydrogen, water, rock (MgSiO3 perovskite) and iron.
6•10−5 55 Cnc e falls between the rock and iron lines, suggesting
a rock-iron composition similar to Earth. The right panel of
Figure 3 shows some theoretical curves based on more de-
Signal Residue
5•10−5 tailed models. In the models of Valencia et al. (2006), for
example, a planet of this mass should have a radius of 1.7-
4•10−5 1.8 R⊕ , within the uncertainty of the measured radius.
4.2. Possibility of an atmosphere
3•10−5 We estimated the maximum possible mass of an atmosphere
in a manner similar to the approach taken by Charbonneau et
2•10−5 al. (2009). We assumed the solid portion of the planet has a ra-
dius of 1.4 R⊕ , which Marcus et al. (2010) argued is the small-
1•10−5 est plausible radius for a planet of this mass, obtained in the
0.0 0.5 1.0 1.5 2.0 limit of maximum stripping of the mantle by giant impacts.
Frequency (cycles day−1) We added an isothermal atmosphere composed of 75% hy-
drogen and 25% helium with a pressure of 1 mbar at a height
F IG . 2.— Box-fitting Least Squares frequency spectrum of the MOST of 1.8 R⊕ (the 1σ upper bound on the measured radius). The
data. Positive peaks indicate detections of candidate transit signals with du- outcome of this calculation was that any atmosphere likely
rations consistent with a near-equatorial transit of 55 Cnc. The strongest peak comprises less than 0.01% of the planet’s mass.
is at the 0.74 d period, and there is no signal at the 2.81 d period. Any atmosphere around 55 Cnc e would be strongly heated,
as the planet is located only 3 R⋆ from the host star. The
R p /R⋆ , the star-to-orbit radius ratio R⋆ /a, the orbital inclina- temperature at the substellar point could be as high as 2970 K
tion i, and the time of midtransit Tc . The orbit was assumed if the planet is tidally locked and the incoming heat remains
to be circular. Uniform priors were adopted for R p /R⋆ , cos i on the dayside. If the heat is redistributed evenly over the
and Tc . Because ingress and egress are not well defined in planet’s entire surface, the equilibrium temperature could be
the data, we used Gaussian priors on the stellar radius and 2100 K, assuming an albedo of zero.
mass, R⋆ = 1.10 ± 0.10 R⊙ and M⋆ = 0.96 ± 0.10 M⊙ . The It is questionable whether an atmosphere could be retained
radius prior is based on the interferometrically measured stel- in such infernal conditions. We estimated the energy-limited
lar radius (van Belle & von Braun 2009). The mass prior is hydrodynamic escape rate using Eqn. (19) of Murray-Clay et
based on the analysis of the stellar spectroscopic properties by al. (2009). To estimate the UV flux we used Eqn. (1) of Ribas
Takeda et al. (2007).12 et al. (2005) for an assumed age of 5 Gyr, giving 1.6 × 104
The likelihood was taken to be exp(−χ2 /2) with the usual
erg s−1 cm−2 . Then, assuming 30% of the incident power of
sum-of-squares definition of χ2 . The 1σ uncertainty in each the ionizing radiation is available to do work on the atmo-
data point was taken to be the root-mean-square (rms) out-
sphere, the escape rate is ∼5 ×109 g s−1 and the total mass
of-transit flux multiplied by a factor β intended to take into
loss over 5 Gyr is ∼0.02 M p , several orders of magnitude
account the time-correlated noise. The factor β is the ratio
larger than maximum atmospheric mass. Thus it seems un-
between the standard deviation of residuals binned to 15 min,
likely that 55 Cnc e retains any primordial low-molecular-
and the standard deviation one would expect based on the un-
weight atmosphere, although it is possible that tectonic activ-
binned data assuming white noise (see, e.g., Pont et al. 2006,
ity replenishes a thin high-molecular-weight atmosphere. No
Carter & Winn 2009). The rms and β values were 90 ppm and
firm conclusions are possible due to the large uncertainties in-
1.31, respectively.
volved, but one observational test would be to measure the
There are 530 data points in the binned light curve, and the
thermal phase curve and the location of the hottest portion of
model has essentially 3 free parameters (depth, duration, and
the planet. An atmospheric wind could act to shift the hot spot
central phase), giving 527 degrees of freedom. The reduction
away from the substellar point (see, e.g., Knutson et al. 2007).
in χ2 by fitting a transit model, as compared to a straight line,
is ∆χ2 = 146, representing a highly significant detection. Ta- 4.3. Comparison with other super-Earths
ble 1 gives the results for the model parameters, based on the 55 Cnc e is one of a growing number of super-Earths with
marginalized posteriors of the Markov chains. measured masses and radii, allowing us to compare their
physical properties and gain clues about their formation and
4. DISCUSSION evolution. The right panel of Figure 3 focuses on the super-
4.1. Comparison to theoretical models Earths and indicates the contours of constant mean density.
Both the mass and radius of 55 Cnc e are known to within The trio of Kepler-10b (Batalha et al. 2011), CoRoT-7b (Léger
10%, providing a valuable example with which to test theo- et al. 2009) and 55 Cnc e all have high densities, while
retical models of super-Earth structure. To provide a broad GJ 1214b (Charbonneau et al. 2009) and Kepler-11d, e, and f
view, the left panel of Figure 3 shows the masses and radii (Lissauer et al. 2011) have much lower densities. A striking
of the transiting exoplanets for which both quantities have contrast exists between 55 Cnc e and Kepler-11e, which have
similar masses but densities differing by a factor of 20.
12 Takeda et al. (2007) advocate a smaller uncertainty, M⋆ = It may be relevant that the higher-density super-Earths are
0.963+0.051 M⊙ , but the same analysis led to R⋆ = 0.930+0.040 M⊙ which
−0.029 −0.030
subject to more intense insolation. They all orbit G stars with
disagrees by 1.6σ with the interferometrically measured radius. Therefore periods <1 day. In contrast, the lower-density Kepler-11 plan-
we enlarged the mass uncertainty to 0.10 M⊙ . ets have periods 10-50 days, and GJ 1214b orbits a much
4. 4 Winn et al. 2011
5
Exoplanets
Solar system
15 K−11e
−3
cm m
−3
g
4 5 gc
0. 1.0
−3
cm
2.0 g
K−11d
Radius [REarth]
Radius [REarth]
10 3
4.0 −3
g cm
K−11f GJ 1214b er
50% wat
8.0 −3
K−11b g cm
2 E arth−like
n water iron frac
tion
5 e maximum 16.0 −3
og C−7b
dr
g cm
hy rock
55 Cnc e
K−10b
iron 1
55 Cnc e
0
1 10 100 1000 2 4 6 8 10 12 14
Mass [MEarth] Mass [MEarth]
F IG . 3.— Masses and radii of transiting exoplanets. Open circles (blue) are previously known transiting planets. The filled circle (red) is 55 Cnc e. The stars
(green) are Solar system planets, for comparison. Left.—Broad view, with curves showing mass-radius relations for pure hydrogen, water ice, silicate (MgSiO3
perovskite) and iron, from Figure 4 of Seager et al. (2007). Right.—Focus on super-Earths, showing contours of constant mean density and a few illustrative
theoretical models: a “water-world” composition with 50% water, 44% silicate mantle and 6% iron core; a nominal “Earth-like” composition with terrestrial
iron/silicon ratio and no volatiles (Valencia et al. 2006, Li & Sasselov, submitted); and the maximum mantle stripping limit (maximum iron fraction, minimum
radius) computed by Marcus et al. (2010).
cooler M dwarf. Perhaps we are witnessing the consequences
of atmospheric escape and mass loss due to strong stellar ir-
radiation. This interpretation is not unique, though, because 6 55 Cnc e
there are other possible routes to producing high-density plan-
8
Visual magnitude
ets, such as giant impacts (Marcus et al. 2010).
10 Corot−7b
4.4. Orbital coplanarity Kepler−10b
12
55 Cnc e is the innermost planet in a system of at least five
planets. If the orbits are coplanar and sufficiently close to 14
90◦ inclination, then multiple planets would transit. Transits Kepler−11
of b and c were ruled out by Fischer et al. (2008).13 How- 16
ever, those nondetections do not lead to constraints on mutual GJ1214b
inclinations. Given the measured inclination for planet e of 18
90◦ ± 9◦ , the other planets in the system could be perfectly 100 1000 10000
aligned with planet e and still fail to transit. Transit depth [ppm]
McArthur et al. (2004) reported an orbital inclination 53◦ ±
6.8◦ for the outermost planet d, based on a preliminary inves- F IG . 4.— Stellar brightness and transit depths. The V band magnitudes
and transit depths (R p /R⋆ )2 of the transiting planets with known masses and
tigation of Hubble Space Telescope astrometry. This would <
radii. Solid symbols are super-Earths (M p ∼ 10 M⊕ ).
imply a strong misalignment between the orbits of d and
e. However, the authors noted that the astrometric dataset 4.5. Potential for follow-up observations
spanned only a limited arc of the planet’s orbit, and no fi-
nal results have yet been announced. Additional astrometric Figure 4 shows an observer’s view of the transiting planets.
measurements and analysis are warranted before delving into Plotted are two parameters directly related to the feasibility of
the interpretation of any orbital misalignment. follow-up observations: stellar brightness and transit depth.
55 Cnc e has a uniquely bright host star, towering above the
13 Our MOST observation might have led to even firmer results for planet
other super-Earth hosts and nearly 2 mag brighter than any
b, since it spanned a full orbit of that planet, but unfortunately no useful
other transit host. Even in the near-infrared, where GJ 1214
data were obtained during the transit window because of a satellite subsystem emits a larger fraction of its luminosity, 55 Cnc is about 5 mag
crash (see Fig. 1). The MOST observation did not coincide with any transit brighter. However, Figure 4 also shows that the transit depth
windows for planets c-f. for 55 Cnc e is among the smallest known. This combination
5. Transits of 55 Cnc e 5
of factors causes the follow-up landscape for 55 Cnc e to differ by Takeda et al. 2007), the stellar variability has been tracked
from that of other planets. for 11 years (Fischer et al. 2008), and there is potential for
The shallow depth makes certain follow-up observations future observations such as the detection of p-mode oscilla-
challenging despite the abundance of photons. To resolve the tions that would help define the stellar properties (see, e.g.,
transit ingress and egress, and thereby improve estimates of Gilliland et al. 2011, Nutzman et al. 2011). Furthermore, the
the planet’s orbital inclination and absolute dimensions, it will brightness of the star has already facilitated the discovery of
be necessary to improve the signal-to-noise ratio in the phased other planets in this system, and continued monitoring has a
light curve. This will require observations of more transits, greater potential to reveal additional bodies than is the case
or the use of larger-aperture telescopes. More daunting, but for fainter stars.
within the realm of possibility, is the detection of occultations Finally, there is some pleasure in being able to point to a
and orbital phase variations that might betray the presence of naked-eye star and know the mass and radius of one of its
an atmosphere. The order of magnitude of those effects is planets.
governed by the parameter (R p /a)2 ∼ 2 × 10−5.
Transit timing constraints on the system’s architecture will
not be easily obtained, given the shallow transit as well as the
small amplitudes of the expected signals. Even planet b, the We thank Laura McKnight and Andrew Howard for
nearest planet to e, is expected to perturb e’s transit epoch by helpful conversations. J.M., D.G., A.M., and S.R. thank
less than 1 s over the course of its 14 d period. The most read- NSERC (Canada) for financial support. T.K. is supported
ily detectable effect may be the Römer delay due to planet d, by a contract to the Canadian Space Agency. R.K. and
which should cause a sinusoidal variation in planet e’s tran- W.W. were supported by the Austrian Science Fund. D.D. is
sit epoch with peak-to-trough amplitude of 12 s and period supported by a FQRNT scholarship. R.D. is supported by a
5191 d. National Science Foundation Graduate Research Fellowship,
On the other hand, follow-up observations of the star itself and D.C.F. by a NASA Hubble Fellowship through grant
are far easier than for other transit hosts, and will continue to HF-51272.01-A. M.H. and J.W. gratefully acknowledge
be rewarding. Already the stellar radius has been measured support from the NASA Origins program through award
interferometrically (van Belle & von Braun 2009), the optical NNX09AB33G.
spectrum has revealed chemical peculiarities (as summarized
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TABLE 1
S YSTEM PARAMETERS FOR 55 C NC E
Parameter Value
Orbital period, P [d] 0.736540 ± 0.000003
Midtransit time [HJD] 2, 455, 607.0553 ± 0.0026
Planet-to-star radius ratio, R p /R⋆ 0.01356 ± 0.00078
Transit duration, first to fourth contact [d] 0.0734 ± 0.0054
Transit ingress or egress duration [d] +0.00031
0.00116−0.00014
Transit impact parameter 0.00 ± 0.45
Orbital inclination, i [deg] 90.0 ± 8.6
Fractional stellar radius, R⋆ /a 0.3278 ± 0.026
Fractional planetary radius, R p /a +0.00053
0.00441−0.00037
Orbital distance, a [AU] 0.01573 ± 0.00054
Planetary mass [M⊕ ] 8.57 ± 0.64
Planetary radius [R⊕ ] 1.63 ± 0.16
Planetary mean density [g cm−3 ] 10.9 ± 3.1
Planetary surface gravity [m s−2 ] 31.7 ± 6.1
N OTE. — These parameters were determined by fitting
the MOST light curve as described in the text, in combina-
tion with external constraints on the stellar reflex velocity K⋆ =
6.1 ± 0.2 m s−1 , stellar mass M⋆ = 0.96 ± 0.10 M⊙ (Takeda
et al. 2007, with an enlarged uncertainty), and stellar radius
R⋆ = 1.10 ± 0.10 R⊙ (van Belle & von Braun 2009). We fur-
ther assumed the orbital eccentricity to be zero, and the limb-
darkening law to be quadratic with fixed coefficients u1 = 0.657
and u2 = 0.115.