The newly discovered planet GJ 1214b is the first known transiting super-Earth requiring a significant atmosphere to explain its observed mass and radius. Models for the structure of this planet predict that it likely possesses a H-He envelope of at least 0.05% of the total mass of the planet. However, models without a significant H-He atmosphere are not entirely ruled out by the available data. Here we explore a range of possible atmospheres for the planet, ranging from solar composition gas, to pure CO_2 or water (steam). We present transmission and emission spectra for each of these cases. We find that, if GJ 1214b possesses a hydrogen-rich atmosphere as expected, then the primary transit depth for such an atmosphere would vary at a level of up to 0.3% as a function of wavelength, relative to the background light of its M-dwarf host star. Observations at this level of precision are potentially obtainable with current space-based instrumentation. Successful detection of the transmission signature of this planet at the ~0.1% level would therefore provide confirmation of the hydrogen-rich nature of the planetary atmosphere. It follows that transmission spectroscopy at this level of precision could provide a first glimpse into answering the question of whether planets in the super-Earth mass regime (1 - 10 M_Earth) more closely resemble large terrestrial planets or small gas giant planets.
We present two new planetary systems found around cool dwarf stars with data from the K2 mission. The first system was found in K2-239 (EPIC 248545986), char- acterized in this work as M3.0V and observed in the 14th campaign of K2. It consists of three Earth-size transiting planets with radii of 1.1, 1.0 and 1.1 R Earth, showing a compact configuration with orbital periods of 5.24, 7.78 and 10.1 days, close to 2:3:4 resonance. The second was found in K2-240 (EPIC 249801827), characterized in this work as M0.5V and observed in the 15th campaign. It consists of two transiting super-Earths with r…
We provide an example of an analysis to explore the optimization of observations of transiting hot jupiters with JWST to characterize their atmospheres, based on a simple three-parameter forward model. We construct expansive forward model sets for eleven hot jupiters, ten of which are relatively well-characterized, exploring a range of parameters such as equilibrium temperature and metallicity, as well as considering host stars over a wide range in brightness. We compute posterior distributions of our model parameters for each planet with all of the available JWST spectroscopic modes and sever…
[Abridged] We have only been able to comprehensively characterize the atmospheres of a handful of transiting planets, because most orbit faint stars. TESS will discover transiting planets orbiting the brightest stars, enabling, in principle, an atmospheric survey of 10^2 to 10^3 bright hot Jupiters and warm sub-Neptunes. Uniform observations of such a statistically significant sample would provide leverage to understand---and learn from---the diversity of short-period planets. We argue that the best way to maximize the scientific returns of TESS is with a follow-up space mission consisting of …
Before an exoplanet transit, atmospheric refraction bends light into the line of sight of an observer. The refracted light forms a stellar mirage, a distorted secondary image of the host star. I model this phenomenon and the resultant out-of-transit flux increase across a comprehensive exoplanetary parameter space. At visible wavelengths, Rayleigh scattering limits the detectability of stellar mirages in most exoplanetary systems with semi-major axes $\lesssim$6 AU. A notable exception is almost any planet orbiting a late M or ultra-cool dwarf star at $\gtrsim$0.5 AU, where the maximum relativ…
Transiting exoplanets provide detailed access to their atmospheres, as the planet's signal can be effectively separated from that of its host star. For transiting exoplanets three fundamental atmospheric measurements are possible: transmission spectra - where atmospheric absorption features are detected across an exoplanets limb during transit, emission spectra - where the day-side average emission of the planet is detected during secondary eclipse events, and phase curves - where the spectral emission of the planet is mapped globally following the planet around its orbit. All of these techniq…
We explore how well James Webb Space Telescope (JWST) spectra will likely constrain bulk atmospheric properties of transiting exoplanets. We start by modeling the atmospheres of archetypal hot Jupiter, warm Neptune, warm sub-Neptune, and cool super-Earth planets with clear, cloudy, or high mean molecular weight atmospheres. Next we simulate the $λ= 1 - 11$ $μ$m transmission and emission spectra of these systems for several JWST instrument modes for single transit and eclipse events. We then perform retrievals to determine how well temperatures and molecular mixing ratios (CH$_4$, CO, CO$_2$, H…
We report the discovery of three small transiting planets orbiting GJ 9827, a bright (K = 7.2) nearby late K-type dwarf star. GJ 9827 hosts a $1.62\pm0.11$ $R_{\rm \oplus}$ super Earth on a 1.2 day period, a $1.269^{+0.087}_{-0.089}$ $R_{\rm \oplus}$ super Earth on a 3.6 day period, and a $2.07\pm0.14$ $R_{\rm \oplus}$ super Earth on a 6.2 day period. The radii of the planets transiting GJ 9827 span the transition between predominantly rocky and gaseous planets, and GJ 9827 b and c fall in or close to the known gap in the radius distribution of small planets between these populations. At a dis…
We highlight how guaranteed time observations (GTOs) and early release science (ERS) will advance understanding of exoplanet atmospheres and provide a glimpse into what transiting exoplanet science will be done with JWST during its first year of operations. These observations of 27 transiting planets will deliver significant insights into the compositions, chemistry, clouds, and thermal profiles of warm-to-hot gas-dominated planets well beyond what we have learned from HST, Spitzer, and other observatories to date. These data and insights will in turn inform our understanding of planet formati…
We present the detection of three super-Earths transiting the cool star LP415-17, monitored by K2 mission in its 13th campaign. High resolution spectra obtained with HARPS-N/TNG showed that the star is a mid-late K dwarf. Using spectral synthesis models we infer its effective temperature, surface gravity and metallicity and subse- quently determined from evolutionary models a stellar radius of 0.58 R Sun. The planets have radii of 1.8, 2.6 and 1.9 R Earth and orbital periods of 6.34, 13.85 and 40.72 days. High resolution images discard any significant contamination by an intervening star in th…
An important goal within the quest for detecting an Earth-like extrasolar planet, will be to identify atmospheric gaseous bio-signatures. Observations of the light transmitted through the Earth's atmosphere, as for an extrasolar planet, will be the first step for future comparisons. We have completed observations of the Earth during a Lunar eclipse, a unique situation similar to that of a transiting planet. We aim at showing what species could be detected in its atmosphere at optical wavelengths, where a lot of photons are available in the masked stellar light. We present observations of the 2…
Kepler-730 is a planetary system hosting a statistically validated hot Jupiter in a 6.49-day orbit and an additional transiting candidate in a 2.85-day orbit. We use spectroscopic radial velocities from the APOGEE-2N instrument, Robo-AO contrast curves, and Gaia distance estimates to statistically validate the planetary nature of the additional Earth-sized candidate. We perform astrophysical false positive probability calculations for the candidate using the available Kepler data and bolster the statistical validation by using radial velocity data to exclude a family of possible binary star so…
Exoplanets with cloud-free, haze-free atmospheres at the pressures probed by transmission spectroscopy represent a valuable opportunity for detailed atmospheric characterization and precise chemical abundance constraints. We present the first optical to infrared (0.3-5 microns) transmission spectrum of the hot Jupiter WASP-62b, measured with Hubble/STIS and Spitzer/IRAC. The spectrum is characterized by a 5.1-sigma detection of Na I absorption at 0.59 microns, in which the pressure-broadened wings of the Na D-lines are observed from space for the first time. A spectral feature at 0.4 microns i…
Transmission spectra contain a wealth of information about the atmospheres of transiting exoplanets. However, large thermal and chemical gradients along the line of sight can lead to biased inferences in atmospheric retrievals. In order to determine how far from the limb plane the atmosphere still impacts the transmission spectrum, we derive a new formula to estimate the opening angle of a planet. This is the angle subtended by the atmospheric region that contributes to the observation along the line of sight, as seen from the planet centre. We benchmark our formula with a 3D Monte-Carlo radia…
This tutorial is an introduction to techniques used to characterize the atmospheres of transiting exoplanets. We intend it to be a useful guide for the undergraduate, graduate student, or postdoctoral scholar who wants to begin research in this field, but who has no prior experience with transiting exoplanets. We begin with a discussion of the properties of exoplanetary systems that allow us to measure exoplanetary spectra, and the principles that underlie transit techniques. Subsequently, we discuss the most favorable wavelengths for observing, and explain the specific techniques of secondary…
(Abridged) In recent years, ground-based high-resolution spectroscopy has become a powerful tool for investigating exoplanet atmospheres. It allows the robust identification of molecular species, and it can be applied to both transiting and non-transiting planets. Radial-velocity measurements of the star HD 179949 indicate the presence of a giant planet companion in a close-in orbit. Here we present the analysis of spectra of the system at 2.3 micron, obtained at a resolution of R~100,000, during three nights of observations with CRIRES at the VLT. We targeted the system while the exoplanet wa…
The relatively recent detections of the first three transiting super-Earths mark the beginning of a subfield within exoplanets that is both fruitful and challenging. The first step into characterizing these objects is to infer their composition given the degenerate character of the problem. The calculations show that Kepler-10b has a composition between an Earth-like and a Mercury-like (enriched in iron) composition. In contrast, GJ 1214b is too large to be solid, and has to have a volatile envelope. Lastly, while three of the four reported mass estimates of CoRoT-7b allow for a rocky composit…
Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as ultracool dwarfs. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disk, there should be a large but hitherto undetected population of terrestrial planets orbiting them - ranging from …
Discoveries from the prime Kepler mission demonstrated that small planets (< 3 Earth-radii) are common outcomes of planet formation. While Kepler detected many such planets, all but a handful orbit faint, distant stars and are not amenable to precise follow up measurements. Here, we report the discovery of two small planets transiting K2-21, a bright (K = 9.4) M0 dwarf located 65$\pm$6 pc from Earth. We detected the transiting planets in photometry collected during Campaign 3 of NASA's K2 mission. Analysis of transit light curves reveals that the planets have small radii compared to their host…
Absorption of stellar Hα by the upper atmosphere of the planet HD189733b has recently been detected by Jensen et al. Motivated by this observation, we have developed a model for atomic hydrogen in the n=2 state and compared the resulting Hα line profile to the observations. The model atmosphere is in hydrostatic balance, as well as thermal and photoionization equilibrium. Collisional and radiative transitions are included in the determination of the n=2 state level population. We find that Hα absorption is dominated by an optical depth τ ~ 1 shell, composed of hydrogen in the metastable 2s sta…
The atmospheric pressure-temperature profiles for transiting giant planets cross a range of chemical transitions. Here we show that the particular shape of these irradiated profiles for warm giant planets below 1300 K lead to striking differences in the behavior of non-equilibrium chemistry compared to brown dwarfs of similar temperatures. Our particular focus is H$_2$O, CO, CH$_4$, CO$_2$, and NH$_3$ in Jupiter- and Neptune-class planets. We show the cooling history of a planet, which depends most significantly on planetary mass and age, can have a dominant effect on abundances in the visible…
We present the confirmation and characterisation of GJ 3473 b (G 50--16, TOI-488.01), a hot Earth-sized planet orbiting an M4 dwarf star, whose transiting signal ($P=1.1980035\pm0.0000018\mathrm{\,d}$) was first detected by the Transiting Exoplanet Survey Satellite (TESS). Through a joint modelling of follow-up radial velocity observations with CARMENES, IRD, and HARPS together with extensive ground-based photometric follow-up observations with LCOGT, MuSCAT, and MuSCAT2, we determined a precise planetary mass, $M_b = 1.86\pm0.30\,\mathrm{M_\oplus},$ and radius, $R_b = {1.264\pm0.050}\,\mathrm…
Using a 3D GCM, we create dynamical model atmospheres of a representative transiting giant exoplanet, HD 209458b. We post-process these atmospheres with an opacity code to obtain transit radius spectra during the primary transit. Using a spectral atmosphere code, we integrate over the face of the planet seen by an observer at various orbital phases and calculate light curves as a function of wavelength and for different photometric bands. The products of this study are generic predictions for the phase variations of a zero-eccentricity giant planet's transit spectrum and of its light curves. W…
Current observations of the atmospheres of close-in exoplanets are predominantly obtained with two techniques: low-resolution spectroscopy with space telescopes and high-resolution spectroscopy from the ground. Although the observables delivered by the two methods are in principle highly complementary, no attempt has ever been made to combine them, perhaps due to the different modeling approaches that are typically used in their interpretation. Here we present the first combined analysis of previously-published dayside spectra of the exoplanet HD 209458b obtained at low resolution with HST/WFC…
Super-Earths and mini-Neptunes exhibit great diversity in their compositional and orbital properties. Their bulk densities span a large range, from those dense enough to be purely rocky to those needing a substantial contribution from volatiles to their volumes. Their orbital configurations range from compact, circular multi-transiting systems like Kepler-11 to systems like our Solar System's terrestrial planets with wider spacings and modest but significant eccentricities and mutual inclinations. Here we investigate whether a continuum of formation conditions resulting from variation in the a…
In this white paper, we assess the potential for JWST to characterize the atmospheres of super-Earth exoplanets, by simulating a range of transiting spectra with different masses and temperatures. Our results are based on a JWST simulator tuned to the expected performance of the workhorse spectroscopic instrument NIRSpec, and is based on the latest exoplanet transit models by Howe & Burrows (2012). This study is especially timely since the observing modes for the science instruments on JWST are finalized (Clampin 2010) and because NASA has selected the TESS mission as an upcoming Explorer. TES…
In the search for life in the cosmos, transiting exoplanets are currently our best targets. In the search for life in the cosmos, transiting exoplanets are currently our best targets. With thousands already detected, our search is entering a new era of discovery with upcoming large telescopes that will look for signs of life in the atmospheres of transiting worlds. However, the universe is dynamic, and which stars in the solar neighborhood have a vantage point to see Earth as a transiting planet and can identify its vibrant biosphere since early human civilizations are unknown. Here we show th…
We report the discovery of the 1.008-day, ultra-short period (USP) super-Earth HD 213885b (TOI-141b) orbiting the bright ($V=7.9$) star HD 213885 (TOI-141, TIC 403224672), detected using photometry from the recently launched TESS mission. Using FEROS, HARPS and CORALIE radial-velocities, we measure a precise mass of $8.8\pm0.6$ $M_\oplus$ for this $1.74 \pm 0.05$ $R_\oplus$ exoplanet, which provides enough information to constrain its bulk composition, which is similar to Earth's but enriched in iron. The radius, mass and stellar irradiation of HD 213885b are, given our data, very similar to 5…
The Kepler mission showed us that planets with sizes between that of Earth and Neptune appear to be the most common type in our Galaxy. These "super-Earths" continue to be of great interest for exoplanet formation, evolution, and composition studies. However, the number of super-Earths with well-constrained mass and radius measurements remains small (40 planets with $σ_{\rm{mass}}<$ 25\%), due in part to the faintness of their host stars causing ground-based mass measurements to be challenging. Recently, three transiting super-Earth planets were detected by the K2 mission around the nearby sta…
We describe the detection of water vapor in the atmosphere of the transiting hot Jupiter KELT-2Ab by treating the star-planet system as a spectroscopic binary with high-resolution, ground-based spectroscopy. We resolve the signal of the planet's motion with deep combined flux observations of the star and the planet. In total, six epochs of Keck NIRSPEC $L$-band observations were obtained, and the full data set was subjected to a cross correlation analysis with a grid of self-consistent atmospheric models. We measure a radial projection of the Keplerian velocity, $K_P$, of 148 $\pm$ 7 km s$^{-1…
We present a super-Earth orbiting close to the inner edge of the habitable zone of the cool dwarf star K2-286 (EPIC 249889081), detected with data from the K2 mission in its $15^{th}$ campaign. The planet has radius of $2.1\pm0.2$ R$_{\oplus}$, near the 1.5 - 2.0 R$_{\oplus}$ gap in the radii distribution. The equilibrium temperature is $347^{+21}_{-11}$ K, cooler than most of the small planets with well measured masses, and the orbital period is $27.359\pm0.005$ days. K2-286, located at a distance of $76.3\pm0.3$ pc, is an M0V star with estimated effective temperature of $3926\pm100$ K, less …
The James Webb Space Telescope (JWST) is nearing its launch date of 2018, and will undoubtedly revolutionize our knowledge of exoplanet atmospheres. While several studies have explored what the limits of the telescope will be in terms of exoplanet characterization, less has been done to specifically identify which observing modes will be most useful for characterizing a diverse range of exoplanetary atmospheres. We use an information content based approach commonly used in the studies of Solar System atmospheres. We develop a system based upon these information content methods to trace the ins…
M dwarf stars, which have masses less than 60 per cent that of the Sun, make up 75 per cent of the population of the stars in the Galaxy [1]. The atmospheres of orbiting Earth-sized planets are observationally accessible via transmission spectroscopy when the planets pass in front of these stars [2,3]. Statistical results suggest that the nearest transiting Earth-sized planet in the liquid-water, habitable zone of an M dwarf star is probably around 10.5 parsecs away [4]. A temperate planet has been discovered orbiting Proxima Centauri, the closest M dwarf [5], but it probably does not transit …
We predict the carbon-to-oxygen (C/O) ratios in the hydrogen-helium envelope and atmospheres of a sample of nearly 50 relatively cool ($T_{\mathrm eq}<$ 1000 K) transiting gas giant planets. The method involves planetary envelope metallicity estimates that use the structure models of Thorngren et al. (2016) and the disk and planetary accretion model of Öberg et al. (2011). We find that nearly all of these planets are strongly metal-enriched which, coupled with the fact that solid material is the main deliverer of metals in the protoplanetary disk, implies that the substellar C/O ratios of thei…
The hundreds of multiple planetary systems discovered by the \textit{Kepler} mission are typically observed to reside in close-in ($\lesssim0.5$ AU), low-eccentricity, and low-inclination orbits. We run N-body experiments to study the effect that unstable outer ($\gtrsim1$ AU) giant planets, whose end orbital configurations resemble those in the Radial Velocity population, have on these close-in multiple super-Earth systems. Our experiments show that the giant planets greatly reduce the multiplicity of the inner super-Earths and the surviving population can have large eccentricities ($e\gtrsim…
Context. The photometric signal we receive from a star hosting a planet is modulated by the variation of the planet signal with its orbital phase. Such phase variations are observed for transiting hot Jupiters with current instrumentation, and have also been measured for one transiting terrestrial planet (Kepler 10 b) and one non-transiting gas giant (Ups A b). Future telescopes (JWST and EChO) will have the capability to measure thermal phase curves of exoplanets including hot rocky planets in transiting and non-transiting configurations, and at different wavelengths. Short-period planets wit…
Water, methane and carbon-monoxide are expected to be among the most abundant molecules besides molecular hydrogen in the hot atmosphere of close-in EGPs. Transit observations in the mid-IR allow the atmospheric content of transiting planets to be determined. We present new primary transit observations of the hot-jupiter HD189733b, obtained simultaneously at 4.5 and 8 micron with IRAC instrument onboard Spitzer. Together with a new refined analysis of previous observations at 3.6 and 5.8 micron using the same instrument, we are able to derive the system parameters, including planet-to-star rad…
We perform modeling investigations to aid in understanding the atmospheres and composition of small planets of ~2-4 Earth radii, which are now known to be common in our galaxy. GJ 1214b is a well studied example whose atmospheric transmission spectrum has been observed by many investigators. Here we take a step back from GJ 1214b to investigate the role that planetary mass, composition, and temperature play in impacting the transmission spectra of these low-mass low-density (LMLD) planets. Under the assumption that these planets accrete modest hydrogen-dominated atmospheres and planetesimals, …
The atmospheric composition of transiting exoplanets can be characterized during transit by spectroscopy. For the transit of an Earth twin, models predict that biogenic $O_2$ and $O_3$ should be detectable, as well as water vapour, a molecule linked to habitability as we know it on Earth. The aim is to measure the Earth radius versus wavelength $λ$ - or the atmosphere thickness $h(λ)$ - at the highest spectral resolution available to fully characterize the signature of Earth seen as a transiting exoplanet. We present observations of the Moon eclipse of 21-12-2010. Seen from the Moon, the Earth…
The energy deposition and redistribution in hot Jupiter atmospheres is not well understood currently, but is a major factor for their evolution and survival. We present a time dependent radiative transfer model for the atmosphere of WASP-18b which is a massive (10 MJup) hot Jupiter (Teq ~ 2400 K) exoplanet orbiting an F6V star with an orbital period of only 0.94 days. Our model includes a simplified parametrisation of the day-to-night energy redistribution by a modulation of the stellar heating mimicking a solid body rotation of the atmosphere. We present the cases with either no rotation at a…
Understanding the evolution of Earth and potentially habitable Earth-like worlds is essential to fathom our origin in the Universe. The search for Earth-like planets in the habitable zone and investigation of their atmospheres with climate and photochemical models is a central focus in exoplanetary science. Taking the evolution of Earth as a reference for Earth-like planets, a central scientific goal is to understand what the interactions were between atmosphere, geology, and biology on early Earth. The Great Oxidation Event (GOE) in Earth's history was certainly caused by their interplay, but…
We present a dimensionless index that quantifies the degree of cloudiness of the atmosphere of a transiting exoplanet. Our cloudiness index is based on measuring the transit radii associated with the line center and wing of the sodium or potassium line. In deriving this index, we revisited the algebraic formulae for inferring the isothermal pressure scale height from transit measurements. We demonstrate that the formulae of Lecavelier et al. and Benneke & Seager are identical: the former is inferring the temperature while assuming a value for the mean molecular mass and the latter is inferring…
A decade ago, the detection of the first transiting extrasolar planet provided a direct constraint on its composition and opened the door to spectroscopic investigations of extrasolar planetary atmospheres. As such characterization studies are feasible only for transiting systems that are both nearby and for which the planet-to-star radius ratio is relatively large, nearby small stars have been surveyed intensively. Doppler studies and microlensing have uncovered a population of planets with minimum masses of 1.9-10 times the Earth's mass (M_Earth), called super-Earths. The first constraint on…
We report the Transiting Exoplanet Survey Satellite discovery of three small planets transiting one of the nearest and brightest M dwarf hosts to date, TOI-270 (TIC 259377017; K-mag 8.3; 22.5 parsec). The M3V-type star is transited by the super-Earth-sized TOI-270 b (1.247+0.089-0.083 R_earth) and the sub-Neptune-sized exoplanets TOI-270 c (2.42+-0.13 R_earth) and TOI-270 d (2.13+-0.12 R_earth). The planets orbit close to a mean-motion resonant chain, with periods (3.36, 5.66, and 11.38 days) near ratios of small integers (5:3 and 2:1). TOI-270 is a prime target for future studies since: 1) it…
We report on the discovery of three transiting planets around GJ~9827. The planets have radii of 1.75$_{-0.12}^{+0.11 }$, 1.36$_{- 0.09 }^{+ 0.09}$, and 2.10$_{- 0.15 }^{+ 0.15 }$~R$_{\oplus}$, and periods of 1.20896, 3.6480, and 6.2014 days, respectively. The detection was made in Campaign 12 observations as part of our K2 survey of nearby stars. GJ~9827 is a $V = 10.39$~mag K6V star at distance of 30.3 parsecs and the nearest star to be found hosting planets by Kepler and K2. The radial velocity follow-up, high resolution imaging, and detection of multiple transiting objects near commensurab…
To date, the ability for observers to reveal the composition or thermal structure of an exoplanet's atmosphere has rested on two techniques: high-contrast direct imaging and time-series observations of transiting exoplanets. The former is currently limited to characterizing young, massive objects while the latter requires near 90 degree orbital inclinations, thus limiting atmospheric studies to a small fraction of the total exoplanet population. Here we present an observational and analysis technique for studying the atmospheres of non-transiting exoplanets that relies on acquiring simultaneou…
At the dawn of the first discovery of exoplanets orbiting sun-like stars in the mid-1990s, few believed that observations of exoplanet atmospheres would ever be possible. After the 2002 Hubble Space Telescope detection of a transiting exoplanet atmosphere, many skeptics discounted it as a one-object, one-method success. Nevertheless, the field is now firmly established, with over two dozen exoplanet atmospheres observed today. Hot Jupiters are the type of exoplanet currently most amenable to study. Highlights include: detection of molecular spectral features; observation of day-night temperatu…
We report the discovery of the super-Earth K2-265 b detected with K2 photometry. The planet orbits a bright (V_mag = 11.1) star of spectral type G8V with a period of 2.37 days. We obtained high-precision follow-up radial velocity measurements from HARPS, and the joint Bayesian analysis showed that K2-265 b has a radius of 1.71 +/- 0.11 R_earth and a mass of 6.54 +/- 0.84 M_earth, corresponding to a bulk density of 7.1 +/- 1.8 g/cm^3 . Composition analysis of the planet reveals an Earth-like, rocky interior, with a rock mass fraction of 80%. The short orbital period and small radius of the plan…
Transit observations have found the majority of exoplanets to date. Spectroscopic observations of transits and eclipses are the most commonly used tool to characterize exoplanet atmospheres and will be used in the search for life. However, an exoplanet's orbit must be aligned with our line of sight to observe a transit. Here we ask, from which stellar vantage points would a distant observer be able to search for life on Earth in the same way? We use the TESS Input Catalog and data from Gaia DR2 to identify the closest stars that could see Earth as a transiting exoplanet: We identify 1,004 Main…
Nitrogen is a biosignature gas that cannot be maintained in its Earth-like ratio with CO$_2$ under abiotic conditions. It has also proven to be notoriously hard to detect at optical and infrared wavelengths. Fortunately, the ultraviolet region, which has only recently started being explored for terrestrial exoplanets, may provide new opportunities to characterise exoplanetary atmospheric nitrogen. In this work, the future prospects for detecting atomic nitrogen absorption lines in the transmission spectrum of an Earth-like planet orbiting in the habitable zone of a Sun-like star with LUVOIR ar…
We present secondary eclipse observations of the highly irradiated transiting brown dwarf KELT-1b. These observations represent the first constraints on the atmospheric dynamics of a highly irradiated brown dwarf, and the atmospheres of irradiated giant planets at high surface gravity. Using the Spitzer Space Telescope, we measure secondary eclipse depths of 0.195+/-0.010% at 3.6um and 0.200+/-0.012% at 4.5um. We also find tentative evidence for the secondary eclipse in the z' band with a depth of 0.049+/-0.023%. These measured eclipse depths are most consistent with an atmosphere model in whi…
We present the discovery of a candidate multiply-transiting system, the first one found in the CoRoT mission. Two transit-like features with periods of 5.11 and 11.76d are detected in the CoRoT light curve, around a main sequence K1V star of r=15.1. If the features are due to transiting planets around the same star, these would correspond to objects of 3.7$\pm$0.4 and 5.0$\pm$0.5 R_earth respectively. Several radial velocities serve to provide an upper limit of 5.7 M_earth for the 5.11~d signal, and to tentatively measure a mass of 28$^{+11}_{-11}$ M_earth for the object transiting with a 11.7…
We present a mass determination for the transiting super-Earth rho 1 Cancri e based on nearly 700 precise radial velocity (RV) measurements. This extensive RV data set consists of data collected by the McDonald Observatory planet search and published data from Lick and Keck observatories (Fischer et al. 2008). We obtained 212 RV measurements with the Tull Coude Spectrograph at the Harlan J. Smith 2.7 m Telescope and combined them with a new Doppler reduction of the 131 spectra that we have taken in 2003-2004 with the High-Resolution-Spectrograph (HRS) at the Hobby-Eberly Telescope (HET) for th…
A Cool Earth-sized Planet Candidate Transiting a Tenth Magnitude K-dwarf From K2
University of Southern Queensland（南昆士兰大学）；Harvard & Smithsonian（哈佛-史密森天体物理中心）；Zooniverse；University of Oxford（牛津大学）；NASA Ames Research Center（美国宇航局艾姆斯研究中心）；Brorfelde Observatory（布罗费尔德天文台）
We have detected transits of the innermost planet "e" orbiting 55 Cnc (V=6.0), based on two weeks of nearly continuous photometric monitoring with the MOST space telescope. The transits 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 0.963_{-0.029}^{+0.051} M_sun and 0.943 +/- 0.010 R_sun, the planet's mass, radius, and mean density are 8.63 +/- 0.35 Mearth, 2.00 +/- 0.14 Rearth, and 5.9_{-1.1}^{+1.5} g/cm^3. The mea…
Planets occur most frequently around cool dwarfs, but only a handful of specific examples are known to orbit the latest-type M stars. Using TESS photometry, we report the discovery of two planets transiting the low-mass star called LP 791-18 (identified by TESS as TOI 736). This star has spectral type M6V, effective temperature 2960 K, and radius 0.17 R_Sun, making it the third-coolest star known to host planets. The two planets straddle the radius gap seen for smaller exoplanets; they include a 1.1 R_Earth planet on a 0.95 day orbit and a 2.3 R_Earth planet on a 5 day orbit. Because the host …
The polarization state of starlight reflected by a planetary atmosphere uniquely reveals coverage, particle size, and composition of aerosols as well as changing cloud patterns. It is not possible to obtain a comparable level of detailed from flux-only observations. Furthermore, polarization observations can probe the atmosphere of planets independently of the orbital geometry (i.e., transiting and non-transiting planets). We show that a high-resolution spectropolarimeter with a broad wavelength coverage, particularly if attached to a large space telescope, would enable simultaneous study of t…
Super-Earths possess low-mass H$_2$/He atmospheres (typically less than 10% by mass). However, the origins of super-Earth atmospheres have not yet been ascertained. We investigate the role of rapid disk clearing by photoevaporation during the formation of super-Earths and their atmospheres. We perform unified simulations of super-Earth formation and atmospheric evolution in evolving disks that consider both photoevaporative winds and magnetically driven disk winds. For the growth mode of planetary cores, we consider two cases in which planetary embryos grow with and without pebble accretion. O…
In this chapter we describe chemistry of the early atmosphere of the Earth during and shortly after its formation where there is little if any geological record. We review the arguments for a secondary origin of the terrestrial atmosphere, that is by outgassing during and/or after accretion rather than by capture of solar nebula gas. Then we discuss sources of volatiles accreted by the Earth using meteorites as analogs for the material present in the solar nebula. The next section reviews heating during accretion of the Earth. Subsequently we describe chemistry of the silicate vapor, steam, an…
