The Earth as an extrasolar transiting planet: Earth's atmospheric composition and thickness revealed by Lunar eclipse observations
Alfred Vidal-Madjar, Luc Arnold, David Ehrenreich, Roger Ferlet, Alain Lecavelier des Etangs, François Bouchy, Damien Segransan, Isabelle Boisse, Guillaume Hébr… 展开作者
Alfred Vidal-Madjar, Luc Arnold, David Ehrenreich, Roger Ferlet, Alain Lecavelier des Etangs, François Bouchy, Damien Segransan, Isabelle Boisse, Guillaume Hébrard, Claire Moutou, Jean-Michel Désert, David K. Sing, Rémy Cabanac, Christian Nitschelm, Xavier Bonfils, Xavier Delfosse, Morgan Desort, Rodrigo F. Díaz, Anne Eggenberger, Thierry Forveille, Anne-Marie Lagrange, Christophe Lovis, Francesco Pepe, Christian Perrier, Frédéric Pont, Nuno C. Santos, Stéphane Udry
备注：
15 pages, 14 figures, 2 tables. Accepted for publication in Astronomy and Astrophysics
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 2008 August 16 Moon eclipse performed with the SOPHIE spectrograph at the Observatoire de Haute-Provence. Locating the spectrograph fibers in the penumbra of the eclipse, the Moon irradiance is then a mix of direct, unabsorbed Sun light and solar light that has passed through the Earth's limb. This mixture essentially reproduces what is recorded during the transit of an extrasolar planet. We report here the clear detection of several Earth atmospheric compounds in the transmission spectra, such as ozone, molecular oxygen, and neutral sodium as well as molecular nitrogen and oxygen through the Rayleigh signature. Moreover, we present a method that allows us to derive the thickness of the atmosphere versus the wavelength for penumbra eclipse observations. We quantitatively evaluate the altitude at which the atmosphere becomes transparent for important species like molecular oxygen and ozone, two species thought to be tightly linked to the presence of life. The molecular detections presented here are an encouraging first attempt, necessary to better prepare for the future of extremely-large telescopes and transiting Earth-like planets. Instruments like SOPHIE will be mandatory when characterizing the atmospheres of transiting Earth-like planets from the ground and searching for bio-marker signatures.
Given the renewed scientific interest in lunar exploration missions, complete understanding of lunar near surface environment and its exosphere under different conditions is of paramount importance. Lunar exosphere has been extensively studied by ground based observations [18,19,20,21,22,23] and hypothesized by different models[1,2,3,4,5,6,7,8,9,10,11,12,13]. In present work, we have discussed overlooked possible sources behind changes in the lunar exosphere when the Moon passes through the penumbra and umbra of the Earth during a lunar eclipse. The dusty turbulent environment due to planetary…
We discuss here a lunar impact flash recorded during the total lunar eclipse that occurred on 2019 January 21, at 4h 41m 38.09 +- 0.01 s UT. This is the first time ever that an impact flash is unambiguously recorded during a lunar eclipse and discussed in the scientific literature, and the first time that lunar impact flash observations in more than two wavelengths are reported. The impact event was observed by different instruments in the framework of the MIDAS survey. It was also spotted by casual observers that were taking images of the eclipse. The flash lasted 0.28 seconds and its peak lu…
Polarization during a lunar eclipse is a forgotten mystery. Coyne & Pellicori (1970) reported the detection of significant polarization during the lunar eclipse on 1968 April 13. Multiple scattering during the first transmission through the Earth's atmosphere was suggested as a possible cause of the polarization, but no conclusive determination was made. No further investigations on polarization during a lunar eclipse are known. We revisit this mystery with an interest in possible application to extrasolar planets, if planetary transmitted light is indeed polarized, it may be possible to inves…
The sunlight reflected from the Moon during a total lunar eclipse has been transmitted through the Earth's atmosphere on the way to the Moon. The combination of multiple scattering and inhomogeneous atmospheric characteristics during that transmission can potentially polarize that light. A similar (although much smaller) effect should also be observable from the atmosphere of a transiting exoplanet. We present the results of polarization observations during the first 15 minutes of totality of the lunar eclipse of 2022 May 16. We find degrees of polarization of 2.1 +/- 0.4 per cent in B, 1.2 +/…
Exomoons and Exorings with the Habitable Worlds Observatory II: Finding Endor with Lunar Eclipses
University of Michigan（密歇根大学）；University of California, San Diego（加州大学圣迭戈分校）；JHU Applied Physics Laboratory（约翰斯·霍普金斯大学应用物理实验室）；University of St Andrews（圣安德鲁斯大学）；Lunar & Planetary Laboratory, University of Arizona（亚利桑那大学月球与行星实验室）；Center for Astrophysics, Harvard & Smithsonian（哈佛-史密森天体物理中心）
A model based on celestial geometry and atmospheric physics predicts the dimming and the color of lunar eclipses. Corresponding visual magnitudes and color indices for eclipses from year 2000 through 2050 are listed. The enlargement of the Earth's umbral shadow reported by observers for over 300 years is explained. The geometrical aspects of the model are the sizes and separations of the Sun, Moon and Earth. Atmospheric effects include refraction, absorption and focusing of sunlight.
We report the results of detailed investigation of the Earth's transmission spectra during the lunar eclipse on UT 2011 December 10. The spectra were taken by using the High Dispersion Spectrograph (HDS) mounted on the Subaru 8.2 m telescope with unprecedented resolutions both in time and wavelength (300 s exposure time in umbra and 160,000 spectral resolution, respectively). In our penumbra and umbra data, we detected the individual absorption lines of O2 and H2O in transmission spectra and found that it became deeper as the eclipse became deeper. It indicates that the sunlight reaching the M…
Laser ranging measurements during the total lunar eclipse on 2010 December 21 verify previously suspected thermal lensing in the retroreflectors left on the lunar surface by the Apollo astronauts. Signal levels during the eclipse far exceeded those historically seen at full moon, and varied over an order of magnitude as the eclipse progressed. These variations can be understood via a straightforward thermal scenario involving solar absorption by a ~50% covering of dust that has accumulated on the front surfaces of the reflectors. The same mechanism can explain the long-term degradation of sign…
With the rapid developments in the exoplanet field, more and more terrestrial exoplanets are being detected. Characterising their atmospheres using transit observations will become a key datum in the quest for detecting an Earth-like exoplanet. The atmospheric transmission spectrum of our Earth will be an ideal template for comparison with future exo-Earth candidates. By observing a lunar eclipse, which offers a similar configuration to that of an exoplanet transit, we have obtained a high resolution and high signal-to-noise ratio transmission spectrum of the Earth's atmosphere. This observati…
The paper contains the result description of the photometric observations of the Moon surface during the total lunar eclipse of June, 15, 2011 conducted in southern Russia and Ukraine in three narrow spectral bands with effective wavelengths equal to 503, 677, and 867 nm. The photometric maps of umbra are built, the radial dependencies of relative brightness are compared with the theoretical ones for gaseous atmosphere. Dark anomalies of umbra are shown and related with the aerosol air pollution of the definite regions above the surface of Earth.
We report Spitzer/IRAC photometry of the transiting giant exoplanet HAT-P-1b during its secondary eclipse. This planet lies near the postulated boundary between the pM and pL-class of hot Jupiters, and is important as a test of models for temperature inversions in hot Jupiter atmospheres. We derive eclipse depths for HAT-P-1b, in units of the stellar flux, that are: 0.080% +/- 0.008%,[3.6um], 0.135% +/- 0.022%,[4.5um],0.203% +/- 0.031%,[5.8um], and $0.238% +/- 0.040%,[8.0um]. These values are best fit using an atmosphere with a modest temperature inversion, intermediate between the archetype i…
The Moon's changeable aspect during a lunar eclipse is largely attributable to variations in the refracted unscattered sunlight absorbed by the terrestrial atmosphere that occur as the satellite crosses the Earth's shadow. The contribution to the Moon's aspect from sunlight scattered at the Earth's terminator is generally deemed minor. However, our analysis of a published spectrum of the 16 August 2008 lunar eclipse shows that diffuse sunlight is a major component of the measured spectrum at wavelengths shorter than 600 nm. The conclusion is supported by two distinct features, namely the spect…
The atmospheres of exoplanets are commonly studied by observing the transit of the planet passing in front of its parent star. The obscuration of part of the stellar disk during a transit will reveal aspects of its surface structure resulting from general centre-to-limb variations (CLVs). These become apparent when forming the ratio between the stellar light in and out of transit. These phenomena can be seen particularly clearly during the progress of a penumbral lunar eclipse, where the Earth transits the solar disk and masks different regions of the solar disk as the eclipse progresses. When…
The lunar impact claimed by Zuluaga et al. (2019) during the total eclipse of 21 January has been discussed widely by his research group, introducing some results from the technique of gravitational ray-tracing. A similar event of magnitude 6 was observed visually by the author during the eclipse of 19 years before, that was published under the name of Padua event (Sigismondi and Imponente, 2000a,b) and a video was obtained independently by Gary Emerson (Cudnik, 2002) in the US at the same time. The remarkable repetition of such a phenomenon after 19 years deserves some investigation about kno…
Context: Detecting moons around exoplanets is a major goal of current and future observatories. Moons are suspected to influence rocky exoplanet habitability, and gaseous exoplanets in stellar habitable zones could harbour abundant and diverse moons to target in the search for extraterrestrial habitats. Exomoons will contribute to exoplanetary signals but are virtually undetectable with current methods. Aims: We identify and analyse traces of exomoons in the temporal variation of total and polarised fluxes of starlight reflected by an Earth-like exoplanet and its spatially unresolved moon acro…
Spectroscopic observations of exoplanets are crucial to infer the composition and properties of their atmospheres. HD 189733b is one of the most extensively studied exoplanets and is a corner stone for hot Jupiter models. In this paper, we report the day-side emission spectrum of HD 189733b in the wavelength range 1.1 to 1.7 $μ$m obtained with the Hubble Space Telescope Wide Field Camera 3 in spatial scan mode. The quality of the data is such that even a straightforward analysis yields a high precision Poisson noise limited spectrum: the median 1-$σ$ uncertainty is 57 ppm per 0.02 $μ$m bin. We…
Due to its absence of an atmosphere and relative geological inertness, the Moon's surface records past impacts of objects from the Solar system and beyond. We examine the prospects for discovering extrasolar material near the lunar surface and predict that its abundance is $\mathcal{O}(10)$ parts-per-million (ppm). The abundances of extrasolar organic carbon and biomolecular building blocks (e.g., amino acids) are estimated to be on the order of $0.1$ ppm and $< 0.1$ parts-per-billion (ppb), respectively. We describe strategies for identifying extrasolar material and potentially detecting extr…
During lunar eclipse of January 21, 2019 a meteoroid impacted the Moon producing a visible light flash. The impact was witnessed by casual observers offering an opportunity to study the phenomenon from multiple geographical locations. We use images and videos collected by observers in 7 countries to estimate the location, impact parameters (speed and incoming direction) and energy of the meteoroid. Using parallax, we achieve determining the impact location at lat. $-29.43^{+0.30}_{-0.21}$, lon. $-67.89^{+0.07}_{-0.09}$ and geocentric distance as 356553 km. After devising and applying a photo-m…
Transiting extrasolar planets provide an opportunity to study the mass-radius relation of planets as well as their internal structure. The existence of a secondary eclipse enables further study of the thermal properties of the the planet by observing at infrared wavelengths. The probability of an observable secondary eclipse depends upon the orbital parameters of the planet, particularly eccentricity and argument of periastron. Here we provide analytical expressions for these probabilities, investigate their properties, and calculate their values for the known extrasolar planets. We furthermor…
Of the 342 planets discovered so far orbiting other stars, 58 "transit" the stellar disk, meaning that they can be detected by a periodic decrease in the starlight flux. The light from the star passes through the atmosphere of the planet, and in a few cases the basic atmospheric composition of the planet can be estimated. As we get closer to finding analogues of Earth, an important consideration toward the characterization of exoplanetary atmospheres is what the transmission spectrum of our planet looks like. Here we report the optical and near-infrared transmission spectrum of the Earth, obta…
Observations of the Earthshine off the Moon allow for the unique opportunity to measure the large-scale Earth atmosphere. Another opportunity is realized during a total lunar eclipse which, if seen from the Moon, is like a transit of the Earth in front of the Sun. We thus aim at transmission spectroscopy of an Earth transit by tracing the solar spectrum during the total lunar eclipse of January 21, 2019. Time series spectra of the Tycho crater were taken with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in its polarimetric mode in…
This work deals with the comparison of different parameters (French/IMCCE and US/JPL ephemerides) used to calculate the extension of the umbral shadow and the location of the centre line in the total solar eclipse that took place on March, 29th 2006. We needed to know the exact points where the predicted duration of the solar eclipse was 0 seconds. This phenomenon allows, observed on this particular position, the measurement of the solar diameter. The work is composed by three parts. In the first one is described the evolution of the lunar theory from Hipparchus to the current theory (Bureau d…
It has been posited that lunar eclipse observations may help predict the in-transit signature of Earth-like extrasolar planets. However, a comparative analysis of the two phenomena addressing in detail the transport of stellar light through the planet's atmosphere has not yet been presented. Here, we proceed with the investigation of both phenomena by making use of a common formulation. Our starting point is a set of previously unpublished near-infrared spectra collected at various phases during the August 2008 lunar eclipse. We then take the formulation to the limit of an infinitely distant o…
We review the problem of the consistency between the observed values of the lunar recession from Lunar Laser Ranging (LLR) and of the increase of the length-of-the-day (LOD). From observations of lunar occultations completed by recent IERS data, we derive a variation rate of the LOD equal to 1.09 ms/cy from 1680 to 2020, which compares well with McCarthy and Babcock (1986) and Sidorenkov (2005). This rate is lower than the mean rate of 1.78 ms/cy derived by Stephenson et al. (2016) on the basis of eclipses in the Antiquity and Middle Age. The difference in the two observed rates starts at the …
Since the radio-frequency emission from planets is expected to be strongly influenced by their interaction with the magnetic field and corona of the host star, the physics of this process can be effectively constrained by making sensitive measurements of the planetary radio emission. Up to now, however, numerous searches for radio emission from extrasolar planets at radio wavelengths have only yielded negative results. Here we report deep radio observations of the nearby Neptune-mass extrasolar transiting planet HAT-P-11b at 150 MHz, using the Giant Meterwave Radio Telescope (GMRT). On July 16…
Chemical kinetics plays an important role in controlling the atmospheric composition of all planetary atmospheres, including those of extrasolar planets. For the hottest exoplanets, the composition can closely follow thermochemical-equilibrium predictions, at least in the visible and infrared photosphere at dayside (eclipse) conditions. However, for atmospheric temperatures < ~2000 K, and in the uppermost atmosphere at any temperature, chemical kinetics matters. The two key mechanisms by which kinetic processes drive an exoplanet atmosphere out of equilibrium are photochemistry and transport-i…
The young star PDS110 in the Ori OB1a association underwent two similar eclipses in 2008 and 2011, each of which lasted for a period of at least 25 days. One plausible explanation for these events is that the star was eclipsed by an unseen giant planet (named PDS110b) circled by a ring system that fills a large fraction of its Hill sphere. Through thousands of numerical simulations of the three-body problem, we constrain the mass and eccentricity of this planet as well the size and inclination of its ring, parameters that are not well determined by the observational data alone. We carried out …
Large-scale Morphology of the Optical F-corona from a Total Solar Eclipse Observation During the Artemis II Lunar Flyby
Tokyo City University（东京都市大学）；Tohoku University（东北大学）；National Astronomical Observatory of Japan（日本国立天文台）；Ishigakijima Astronomical Observatory（石垣岛天文台）
We observed the 2019 January total lunar eclipse with the Hubble Space Telescope's STIS spectrograph to obtain the first near-UV (1700-3200 $Å$) observation of Earth as a transiting exoplanet. The observatories and instruments that will be able to perform transmission spectroscopy of exo-Earths are beginning to be planned, and characterizing the transmission spectrum of Earth is vital to ensuring that key spectral features (e.g., ozone, or O$_3$) are appropriately captured in mission concept studies. O$_3$ is photochemically produced from O$_2$, a product of the dominant metabolism on Earth to…
The light curve of 1SWASP J140747.93-394542.6, a $\sim$16 Myr old star in the Sco-Cen OB association, underwent a complex series of deep eclipses that lasted 56 days, centered on April 2007. This light curve is interpreted as the transit of a giant ring system that is filling up a fraction of the Hill sphere of an unseen secondary companion, J1407b. We fit the light curve with a model of an azimuthally symmetric ring system, including spatial scales down to the temporal limit set by the star's diameter and relative velocity. The best ring model has 37 rings and extends out to a radius of 0.6 A…
In this paper we present the high resolution spectral observations of the fragment of lunar surface during the total lunar eclipse of December 10, 2011. The observations were carried out with the fiber-fed echelle spectrograph at 1.2-m telescope in Kourovka Astronomical observatory (Ural mountains, central Russia). The observed radiation is transferred by tangent trajectory through the southern polar stratosphere before the reflection from the Moon and spectra contain a number of absorption bands of atmospheric gases (O2, O3, O4, NO2, H2O). High resolution analysis of three O2 bands and O4 abs…
<abridged> The large relative sizes of circumstellar and circumplanetary disks imply that they might be seen in eclipse in stellar light curves. We estimate that a survey of ~10^4 young (~10 Myr old) post-accretion pre-MS stars monitored for ~10 years should yield at least a few deep eclipses from circumplanetary disks and disks surrounding low mass companion stars. We present photometric and spectroscopic data for a pre-MS K5 star (1SWASP J140747.93-394542.6), a newly discovered ~0.9 Msun member of the ~16 Myr-old Upper Cen-Lup subgroup of Sco-Cen at a kinematic distance of 128 pc. SuperWASP …
The obscuration of a celestial body that covers another one in the background will be called a ``hierarchical eclipse''. The most obvious case is that a star or a planet will be hidden from sight by the moon during a lunar eclipse. Four objects of the solar system will line up then. We investigate this phenomenon with respect to the region of visibility and periodicity. There exists a parallax field constraining the chances for observation. A historic account from the Middle Ages is preserved that we analyse from different viewing angles. Furthermore, we provide a list of events from 0 to 4000…
We examine in detail 15 Babylonian observations of lunar appulses and occultations made between 80 and 419 BC for the purpose of setting useful limits on Earth's clock error, as quantified by $Δ$T, the difference between Terrestrial Time and Universal time. Our results are generally in agreement with reconstructions of $Δ$T using untimed solar eclipse observations from the same period. We suggest a revised version of the simple quadratic fit to $Δ$T in light of the new results.
Solar eclipse is an unique opportunity to study the lower ionospheric variabilities under a controlled perturbation when the solar ultraviolet and X-ray are temporally occulted by the lunar disk. Sub-ionospheric Very Low Frequency (VLF) radio signal displays the ionospheric response of solar eclipse by modulating its amplitude and phase. During the Total Solar Eclipse (TSE) on August 21, 2017 in North America, data was recorded by a number of receivers as presented in public archive. Out of these, two receiving stations YADA in McBaine and K5TD in Tulsa could procure a reasonable quality of no…
We report on the detection of the secondary eclipse of the very-hot Jupiter OGLE-TR-56b from combined z-band time series photometry obtained with the VLT and Magellan telescopes. We measure a flux decrement of 0.0363+/-0.0091 percent from the combined Magellan and VLT datasets, which indicates a blackbody brightness temperature of 2718 (+127/-107) K, a very low albedo, and a small incident radiation redistribution factor, indicating a lack of strong winds in the planet's atmosphere. The measured secondary depth is consistent with thermal emission, but our precision is not sufficient to disting…
We report a sensitive search for meter-wavelength emission at 150 MHz from two prominent transiting extrasolar planets, HD189733b and HD209458b. To distinguish any planetary emission from possible stellar or background contributions, we monitored these systems just prior to, during, and after the planet's eclipse behind the host star. No emission was detected from HD209458b with a 3-sigma upper limit of 3.6 mJy. For HD189733b we obtain a 3-sigma upper limit of 2.1 mJy and a marginal 2.7-sigma detection of about 1.9+/-0.7 mJy from a direction just 13" from the star's coordinates (i.e., within t…
We present photometry of the extrasolar planet WASP-5b in the 3.6 and 4.5 micron bands taken with the Spitzer Space Telescope's Infrared Array Camera as part of the extended warm mission. By examining the depth of the planet's secondary eclipse at these two wavelengths, we can place joint constraints on the planet's atmospheric pressure-temperature profile and chemistry. We measure secondary eclipse depths of 0.197% +/- 0.028% and 0.227% +/- 0.025% in the 3.6 micron and 4.5 micron bands, respectively. Our observations are best matched by models showing a hot dayside and, depending on our choic…
The search for extrasolar rocky planets has already found the first transiting rocky super-Earth, Corot 7b, with a surface temperature that allows for magma oceans. Here we ask if we could distinguish rocky planets with recent major volcanism by remote observation. We develop a model for volcanic eruptions on an Earth-like exoplanet based on the present day Earth, derive the observable features in emergent and transmission spectra for multiple scenarios of gas distribution and cloudcover. We calculate the observation time needed to detect explosive volcanism on exoplanets in primary as well as…
We report a sensitive search for meter-wavelength emission at 244 and 614 MHz from HD189733b, the nearest known extrasolar transiting planet of `hot-Jupiter' type. To discriminate any planetary emission from possible stellar or background contributions, we observed the system for 7.7 hours encompassing the planet's eclipse behind the host star. These GMRT observations provide very low (3 sigma) upper limits of 2 mJy at 244 MHz and 160 micro-Jy at 614 MHz. These limits are, respectively, about 40 and 500 times deeper than those reported recently at a nearby frequency of 340 MHz. Possible explan…
We derive the first secondary eclipse map of an exoplanet, HD 189733b, based on Spitzer IRAC 8 micron data. We develop two complementary techniques for deriving the two dimensional planet intensity: regularized slice mapping and spherical harmonic mapping. Both techniques give similar derived intensity maps for the infrared day-side flux of the planet, while the spherical harmonic method can be extended to include phase variation data which better constrain the map. The longitudinal offset of the day-side hot spot is consistent with that found in prior studies, strengthening the claim of super…
We formulated tidal decay lifetimes for hypothetical moons orbiting extrasolar planets with both lunar and stellar tides. Previous work neglected the effect of lunar tides on planet rotation, and are therefore applicable only to systems in which the moon's mass is much less than that of the planet. This work, in contrast, can be applied to the relatively large moons that might be detected around newly-discovered Neptune-mass and super-Earth planets. We conclude that moons are more stable when the planet/moon systems are further from the parent star, the planets are heavier, or the parent stars…
Long-period transiting exoplanets provide an opportunity to study the mass-radius relation and internal structure of extrasolar planets. Their studies grant insights into planetary evolution akin to the Solar System planets, which, in contrast to hot Jupiters, are not constantly exposed to the intense radiation of their parent stars. Observations of secondary eclipses allow investigations of exoplanet temperatures and large-scale exo-atmospheric properties. In this short paper, we elaborate on, and calculate, probabilities of secondary eclipses for given orbital parameters, both in the presenc…
We present our analysis of the red-channel CoRoT data of CoRoT-2b. A deep secondary eclipse is detected at a level of 1.02+-0.20 x10-4, which suggests that all of the planet-signal detected previously in white light by Alonso et al. (2009) originates from the red channel. CoRoT-2b is the coolest exoplanet that has been detected in the optical so far. In contrast to the other planets, its measured brightness temperature of 2170+-55 K is significantly higher than its maximum hemisphere-averaged effective day-side temperature. However, it is not expected that a hot Jupiter radiates as a black bod…
We investigate the anomalies in the Earth - Moon system using ancient eclipse data. We identify nine groups of anomalous eclipses between 400 and 1800 AD recorded in parts of India that should have completely missed the subcontinent as per NASA simulations (Espenak and Meeus, 2011). We show that the typical correction to the lunar location required to reconcile the anomalous eclipses is relatively small and consistent with the fluctuations in the length of day that are observed in recent periods. We then investigate the change in Earth's moment of inertia due to differential acceleration of la…
We have discovered that Europa, Ganymede and Callisto are bright around 1.5 μm even when not directly lit by sunlight, based on observations from the Hubble Space Telescope and the Subaru Telescope. The observations were conducted with non-sidereal tracking on Jupiter outside of the field of view to reduce the stray light subtraction uncertainty due to the close proximity of Jupiter. Their eclipsed luminosity was $10^{-6}$-$10^{-7}$ of their uneclipsed brightness, which is low enough that this phenomenon has been undiscovered until now. In addition, Europa in eclipse was <1/10 of the others at…
Chemical disequilibrium has recently become a relevant topic in the study of the atmospheres of of transiting extrasolar planets, brown dwarfs, and directly imaged exoplanets. We present a new way of assessing whether or not a Jovian-like atmosphere is in chemical disequilibrium from observations of detectable or inferred gases such as H$_2$O, CH$_4$, CO, and H$_2$. Our hypothesis, based on previous kinetic modeling studies, is that cooler atmospheres will show stronger signs of disequilibrium than hotter atmospheres. We verify this with chemistry-transport models and show that planets with te…
Transiting exoplanets provide access to data to study the mass-radius relation and internal structure of extrasolar planets. Long-period transiting planets allow insight into planetary environments similar to the Solar System where, in contrast to hot Jupiters, planets are not constantly exposed to the intense radiation of their parent stars. Observations of secondary eclipses additionally permit studies of exoplanet temperatures and large-scale exo-atmospheric properties. We show how transit and eclipse probabilities are related to planet-star system geometries, particularly for long-period, …
Planetary rotation rates and obliquities provide information regarding the history of planet formation, but have not yet been measured for evolved extrasolar planets. Here we investigate the theoretical and observational perspective of the Rossiter-McLauglin effect during secondary eclipse (RMse) ingress and egress for transiting exoplanets. Near secondary eclipse, when the planet passes behind the parent star, the star sequentially obscures light from the approaching and receding parts of the rotating planetary surface. The temporal block of light emerging from the approaching (blue-shifted) …
The detection of extrasolar planets' atmospheres requires very demanding observations. For planets that can not be spatially separated from their host stars, i.e. the vast majority of planets, the transiting planets are the only ones allowing to probe their atmospheres. This is possible from transmission spectroscopy or from measurements taken during secondary eclipse. An alternative is the measurement of the Rossiter-McLaughlin-effect, which is sensitive to the size of the planetary radius. Since the radius is wavelength-dependent due to contributions of strong planetary absorption lines, thi…
Thousands of extrasolar planets have been discovered, and it is clear that the galactic planetary census draws on a diversity greatly exceeding that exhibited by the solar system's planets. We review significant landmarks in the chronology of extrasolar planet detection, and we give an overview of the varied observational techniques that are brought to bear. We then discuss the properties of the currently known distribution, using the mass-period diagram as a guide to delineating hot Jupiters, eccentric giant planets, and a third, highly populous, category that we term "ungiants", planets havi…
We present photometry of the giant extrasolar planet WASP-4b at 3.6 and 4.5 micron taken with the Infrared Array Camera on board the Spitzer Space Telescope as part of Spitzer's extended warm mission. We find secondary eclipse depths of 0.319+/-0.031% and 0.343+/-0.027% for the 3.6 and 4.5 micron bands, respectively and show model emission spectra and pressure-temperature profiles for the planetary atmosphere. These eclipse depths are well fit by model emission spectra with water and other molecules in absorption, similar to those used for TrES-3 and HD 189733b. Depending on our choice of mode…
Secondary eclipses are a powerful tool to measure directly the thermal emission from extrasolar planets, and to constrain their type and physical parameters. We started a project to obtain reliable broad-band measurements of the thermal emission of transiting exoplanets. Ground-based high-cadence near-infrared relative photometry was used to obtain sub-millimagnitude precision light curve of a secondary eclipse of WASP-4b -- a 1.12 M_J hot Jupiter on a 1.34 day orbit around G7V star. The data show a clear ~10-σdetection of the planet's thermal emission at 2.2 μm. The calculated thermal emissio…
Although conjunctions and oppositions frequently occur in planetary systems, eclipse-related phenomena are usually described from an Earth-centric perspective. Space missions to different parts of the Solar system, as well as the mounting number of known exo-planets in habitable zones and the possibility of sending featherweight robot spacecraft to them, prompt broader considerations. Here, we derive the geometry of eclipses, transits and occultations from a primarily exo-Earth viewpoint, and apply the formulation to the Solar system and three types of three-body extrasolar planetary systems: …
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…
Context: Secondary eclipse measurements of transiting extrasolar planets with the Spitzer Space Telescope have yielded several direct detections of thermal exoplanet light. Since Spitzer operates at wavelengths longward of 3.6 um, arguably one of the most interesting parts of the planet spectrum (from 1 to 3 um) is inaccessible with this satellite. This region is at the peak of the planet's spectral energy distribution and is also the regime where molecular absorption bands can significantly influence the measured emission. Aims: So far, 2.2 um K-band secondary eclipse measurements, which are …
