Benjamin Charnay
A5038874544- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Planetary Science and Exploration
- Atmospheric Ozone and Climate
- Astronomical Observations and Instrumentation
- Geology and Paleoclimatology Research
- Solar and Space Plasma Dynamics
- Scientific Research and Discoveries
- Space Exploration and Technology
- Geomagnetism and Paleomagnetism Studies
- Spectroscopy and Laser Applications
- Atmospheric and Environmental Gas Dynamics
- Spacecraft and Cryogenic Technologies
- Isotope Analysis in Ecology
- Adaptive optics and wavefront sensing
- Gamma-ray bursts and supernovae
- Methane Hydrates and Related Phenomena
- Calibration and Measurement Techniques
- Geophysics and Gravity Measurements
- Hydrocarbon exploration and reservoir analysis
- Space Science and Extraterrestrial Life
- Spacecraft Design and Technology
- Spacecraft Dynamics and Control
Stanford University
2023-2025
Observatoire de Paris
2016-2024
Université Paris Cité
2017-2024
Laboratoire d’études spatiales et d’instrumentation en astrophysique
2017-2024
Centre National de la Recherche Scientifique
2014-2024
Sorbonne Université
2014-2024
Université Paris Sciences et Lettres
2017-2024
Université de Versailles Saint-Quentin-en-Yvelines
2017-2024
Sorbonne Paris Cité
2017-2024
Janssen (France)
2017-2024
The SHINE program is a large high-contrast near-infrared survey of 600 young, nearby stars. It aimed at searching for and characterizing new planetary systems using VLT/SPHERE's unprecedented high-angular resolution imaging capabilities. also intends placing statistical constraints on the occurrence orbital properties giant planet population orbits as function stellar host mass age to test formation theories. We use IRDIS dual-band imager IFS integral field spectrograph SPHERE acquire...
The inner edge of the classical habitable zone is often defined by critical flux needed to trigger runaway greenhouse instability. This 1D notion a flux, however, may not be so relevant for inhomogeneously irradiated planets, or when water content limited (land planets). Here, based on results from our 3D global climate model, we find that circulation pattern can shift super-rotation stellar/anti stellar equatorial Rossby deformation radius significantly exceeds planetary radius. Using...
Aims: We aim to characterize the orbital and atmospheric properties of PDS 70 b, which was first identified on May 2015 in course SHINE survey with SPHERE, extreme adaptive-optics instrument at VLT. Methods: obtained new deep SPHERE/IRDIS imaging SPHERE/IFS spectroscopic observations b. The astrometric baseline now covers 6 years allows us perform an analysis. For time, we present spectrophotometry young planet almost entire near-infrared range (0.96 3.8 micrometer). use different models...
Context. Clouds are ubiquitous in exoplanet atmospheres and they represent a challenge for the model interpretation of their spectra. When generating large number spectra, complex cloud models often prove too costly numerically, whereas more efficient may be overly simplified. Aims. We aim to constrain atmospheric properties directly imaged planet HR 8799e with free retrieval approach. Methods. used our radiative transfer code petitRADTRANS which we coupled PyMultiNest tool. added effect...
Abstract Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on nightside molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum hot Jupiter WASP-43b measured from 5 μm to 12 JWST’s Mid-Infrared Instrument. The spectra reveal large day–night temperature contrast (with...
Abstract The two-planet transiting system LHS 1140 has been extensively observed since its discovery in 2017, notably with Spitzer, HST, TESS, and ESPRESSO, placing strong constraints on the parameters of M4.5 host star small temperate exoplanets, b c. Here, we reanalyze ESPRESSO observations novel line-by-line framework designed to fully exploit radial velocity content a stellar spectrum while being resilient outlier measurements. improved velocities, combined updated parameters,...
It has been suggested that the recently discovered exoplanet GJ581d might be able to support liquid water due its relatively low mass and orbital distance. However, receives 35% less stellar energy than Mars is probably locked in tidal resonance, with extremely insolation at poles possibly a permanent night side. Under such conditions, it unknown whether any habitable climate on planet would withstand global glaciation / or atmospheric collapse. Here we present three-dimensional simulations...
Recognizing whether a planet can support life is primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations yet dramatically phase Earth's history, when atmosphere contained Titan-like organic-rich haze. Prior work claimed haze-rich Archean Earth (3.8-2.5 billion years ago) would be frozen due to...
The warm sub-Neptune GJ1214b has a featureless transit spectrum which may be due to the presence of high and thick clouds or haze. Here, we simulate atmosphere with 3D General Circulation Model for cloudy hydrogen-dominated atmospheres, including cloud radiative effects. We show that atmospheric circulation is strong enough transport micrometric particles upper generally leads minimum at equator. By scattering stellar light, increase planetary albedo 0.4-0.6 cool below 1 mbar. However,...
To date, infrared interferometry at best achieved contrast ratios of a few times $10^{-4}$ on bright targets. GRAVITY, with its dual-field mode, is now capable high observations, enabling the direct observation exoplanets. We demonstrate technique HR8799, young planetary system composed four known giant used GRAVITY fringe tracker to lock fringes central star, and integrated off-axis HR8799e planet situated 390 mas from star. Data reduction included post-processing remove flux leaking star...
We quantify the amount of nitrogen oxides (NOx) produced through lightning and photochemical processes in Hadean atmosphere to be available ocean for emergence life. Atmospherically generated nitrate (NO3-) nitrite (NO2-) are most attractive high-potential electron acceptors pulling enabling crucial redox reactions autotrophic metabolic pathways at submarine alkaline hydrothermal vents. The atmosphere, dominated by CO2 N2, will produce nitric oxide (NO) when shocked lightning. Photochemical...
Transmission spectroscopy provides us with information on the atmospheric properties at limb, which is often intuitively assumed to be a narrow annulus around planet. Consequently, studies have focused effect of horizontal heterogeneities along limb. Here we demonstrate that region probed in transmission -- limb extends significantly toward day and night sides We show strong day-night thermal compositional gradients expected synchronous exoplanets create sufficient across result important...
Different solutions have been proposed to solve the "faint young Sun problem", defined by fact that Earth was not fully frozen during Archean despite fainter Sun. Most previous studies were performed with simple 1-D radiative convective models and did account well for clouds ice-albedo feedback or atmospheric oceanic transport of energy. We apply a global climate model (GCM) test different faint problem. explore effect greenhouse gases (CO2 CH4), pressure, cloud droplet size, land...
The substellar companion HD206893b has recently been discovered by direct imaging of its disc-bearing host star with the SPHERE instrument. We investigate atypical properties companion, which reddest near-infrared colours among all known objects, either orbiting a or isolated, and we provide comprehensive characterisation star-disc-companion system. conducted follow-up adaptive optics spectro-imaging SPHERE, multiinstrument star. obtain R=30 spectrum from 0.95 to 1.64 micron additional...
Methods used to detect giant exoplanets can be broadly divided into two categories: indirect and direct. Indirect methods are more sensitive planets with a small orbital period, whereas direct detection is orbiting at large distance from their host star. %, thus on long period. This dichotomy makes it difficult combine the techniques single target once. Simultaneous measurements made by offer possibility of determining mass luminosity method testing formation models. Here, we aim show how...
We present K-band interferometric observations of the PDS 70 protoplanets along with their host star using VLTI/GRAVITY. obtained spectra and 100 $\mu$as precision astrometry both b c in two epochs, as well spatially resolving hot inner disk around star. Rejecting unstable orbits, we found a nonzero eccentricity for $0.17 \pm 0.06$, near-circular orbit c, an orbital configuration that is consistent planets migrating into 2:1 mean motion resonance. Enforcing dynamical stability, 95% upper...
We analyse the transmission and emission spectra of ultra-hot Jupiter WASP-76b, observed with G141 grism Hubble Space Telescope's Wide Field Camera 3 (WFC3). reduce fit raw data for each observation using open-source software Iraclis before performing a fully Bayesian retrieval publicly available analysis suite TauRex 3. Previous studies WFC3 WASP-76 b found hints titanium oxide (TiO) vanadium (VO) or non-grey clouds. Accounting fainter stellar companion to WASP-76, we reanalyse this show...
Abstract This paper presents the atmospheric characterization of three large, gaseous planets: WASP-127 b, WASP-79 and WASP-62 b. We analyzed spectroscopic data obtained with G141 grism (1.088–1.68 μ m) Wide Field Camera 3 on board Hubble Space Telescope using Iraclis pipeline TauREx3 retrieval code, both which are publicly available. For is least dense planet discovered so far located in short-period Neptune desert, our results found strong water absorption corresponding to an abundance...
Aims. We aim to demonstrate that the presence and mass of an exoplanet can now be effectively derived from astrometry another exoplanet. Methods. combined previous β Pictoris b with a new set observations GRAVITY interferometer. The orbital motion is fit using Markov chain Monte Carlo simulations in Jacobi coordinates. inner planet, c, was also reobserved at separation 96 mas, confirming estimations. Results. From planet only, we (i) detect c (ii) constrain its 10.04 −3.10 +4.53 M Jup . If...
While small Neptune-like planets are among the most abundant exoplanets, our understanding of their atmospheric structure and dynamics remains sparse. In particular, many unknowns remain regarding way moist convection works in these atmospheres, where condensable species heavier than non-condensable background gas. it has been predicted that could cease above some threshold abundance species, this prediction is based on simple linear analysis relies strong assumptions saturation atmosphere....
With four companions at separations from 16 to 71 au, HR 8799 is a unique target for direct imaging, presenting an opportunity the comparative study of exoplanets with shared formation history. Combining new VLTI/GRAVITY observations obtained within ExoGRAVITY program archival data, we perform systematic atmospheric characterisation all planets. We explore different levels model flexibility understand temperature structure, chemistry and clouds each planet using both petitRADTRANS retrievals...
Abstract LHS 1140 b is the second-closest temperate transiting planet to Earth with an equilibrium temperature low enough support surface liquid water. At 1.730 ± 0.025 R ⊕ , falls within radius valley separating H 2 -rich mini-Neptunes from rocky super-Earths. Recent mass and revisions indicate a bulk density significantly lower than expected for Earth-like interior, suggesting that could be either mini-Neptune small envelope of hydrogen (∼0.1% by mass) or water world (9%–19% mass)....