An extended hydrogen envelope of the extremely hot giant exoplanet KELT-9b

Abstract

Giant exoplanets orbiting close to their host stars have high temperatures because of the immense stellar irradiation which they receive. The extreme energy input leads to the expansion of the atmosphere and the escape of neutral hydrogen. A particularly intriguing case among the hot giant planets is KELT-9b -- an exoplanet orbiting very close to an early A-type star with the highest temperature (~4600 K at day-side) among all the exoplanets known so far. The atmospheric composition and dynamic of such a unique planet have been unknown. Here we report the first detection of an extended hot hydrogen atmosphere around KELT-9b. The detection was achieved by measuring the atomic hydrogen absorption during transit with the Balmer Hα line, which is unusually strong mainly due to the high level of extreme-ultraviolet radiation from the star. We detected a significant wavelength shift of the Hα absorption which is mostly attributed to the planetary orbital motion. The obtained transmission spectrum has a significant line contrast (1.15% extra absorption at the Hα line centre). The observation implies that the effective radius at the Hα line centre is ~1.64 times the size of the planetary radius, indicating the planet has a largely extended hydrogen envelope close to the size of the Roche lobe (1.91 Rplanet) and is probably undergoing dramatic atmosphere escape.

arXiv comment18 pages, 3 figures, 4 supplementary figures. Published in Nature Astronomy on 2 July 2018. Online published: http://www.nature.com/articles/s41550-018-0503-3

References in corpus (26)

• emcee: The MCMC Hammer
• The orbital motion, absolute mass, and high-altitude winds of exoplanet HD209458b
• A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b
• Spectroscopy Made Easy: Evolution
• Spectrally resolved detection of sodium in the atmosphere of HD189733b with the HARPS spectrograph
• The On/Off Nature of Star-Planet Interactions
• A giant planet undergoing extreme ultraviolet irradiation by its hot massive-star host
• A diagram for the evaporation status of extrasolar planets
• Rotation and winds of exoplanet HD 189733 b measured with high-dispersion transmission spectroscopy
• Temporal variations in the evaporating atmosphere of the exoplanet HD 189733b
• Spatially resolved eastward winds and rotation of HD 189733b
• Simulating the escaping atmospheres of hot gas planets in the solar neighborhood
• The long egress of GJ~436b's giant exosphere
• A Detection Of H-alpha In An Exoplanetary Exosphere
• Detection of sodium in the atmosphere of WASP-69b
• The center-to-limb variation across the Fraunhofer lines of HD 189733; Sampling the stellar spectrum using a transiting planet
• Optical hydrogen absorption consistent with a thin bow shock leading the hot Jupiter HD 189733b
• The effect of the stellar absorption line centre-to-limb variation on exoplanet transmission spectrum observations
• A decade of H$\alpha$ transits for HD 189733 b: stellar activity versus absorption in the extended atmosphere
• The origin of the excess transit absorption in the HD 189733 system: planet or star?
• A Model of the H$\alpha$ and Na Transmission Spectrum of HD 189733b
• High resolution transmission spectrum of the Earth's atmosphere -- Seeing Earth as an exoplanet using a lunar eclipse
• Variation in the pre-transit Balmer line signal around the hot Jupiter HD 189733 b
• The centre-to-limb variations of solar Fraunhofer lines imprinted upon lunar eclipse spectra - Implications for exoplanet transit observations
• Hα Absorption in Transiting Exoplanet Atmospheres
• Detection of a spectroscopic transit by the planet orbiting the star HD209458

Cited by in corpus (143)

• Exoplanetary Atmospheres: Key Insights, Challenges and Prospects
• Ground-based detection of an extended helium atmosphere in the Saturn-mass exoplanet WASP-69b
• A spectral survey of an ultra-hot Jupiter: Detection of metals in the transmission spectrum of KELT-9 b
• The HST PanCET Program: Exospheric Mg II and Fe II in the Near-UV transmission spectrum of WASP-121b using Jitter Decorrelation
• Atmospheric characterization of the ultra-hot Jupiter MASCARA-2b/KELT-20b
• Detection of He I $\lambda 10830$ Å absorption on HD 189733 b with CARMENES high-resolution transmission spectroscopy
• Atmospheric Rossiter-McLaughlin effect and transmission spectroscopy of WASP-121b with ESPRESSO
• Neutral Iron Emission Lines From The Day-side Of KELT-9b -- The GAPS Programme With HARPS-N At TNG XX
• The evolution of the solar wind
• Ionized calcium in the atmospheres of two ultra-hot exoplanets WASP-33b and KELT-9b
• Photoevaporation vs. core-powered mass-loss: model comparison with the 3D radius gap
• Atmospheric dynamics and the variable transit of KELT-9 b
• Conclusive evidence for a population of water-worlds around M-dwarfs remains elusive
• A New Window into Planet Formation and Migration: Refractory-to-Volatile Elemental Ratios in Ultra-hot Jupiters
• Atmospheric Regimes and Trends on Exoplanets and Brown Dwarfs
• Decomposing the Iron Cross-Correlation Signal of the Ultra-Hot Jupiter WASP-76b in Transmission using 3D Monte-Carlo Radiative Transfer
• Mass loss rate and local thermodynamic state of KELT-9 b thermosphere from the hydrogen Balmer series
• An Atomic Spectral Survey of WASP-76b: Resolving Chemical Gradients and Asymmetries
• Detection of neutral atomic species in the ultra-hot jupiter WASP-121b
• Confirmation of WASP-107b's extended Helium atmosphere with Keck II/NIRSPEC
• Searching for Thermal Inversion Agents in the Transmission Spectrum of MASCARA-2b/KELT-20b: Detection of Neutral Iron and Ionised Calcium H$\&$K Lines
• Modelling the He I triplet absorption at 10830 Angstroms in the atmosphere of HD 209458 b
• Detection of Na, K, and H$\alpha$ absorption in the atmosphere of WASP-52b using ESPRESSO
• Detection of ionized calcium in the atmosphere of the ultra-hot Jupiter KELT-9b
• Multiple water band detections in the CARMENES near-infrared transmission spectrum of HD 189733 b
• Confirmation of Asymmetric Iron Absorption in WASP-76b with HARPS
• The GAPS programme at TNG XXII. The GIARPS view of the extended helium atmosphere of HD189733 b accounting for stellar activity
• The atmosphere of HD 209458b seen with ESPRESSO. No detectable planetary absorptions at high resolution
• A temperature inversion with atomic iron in the ultra-hot dayside atmosphere of WASP-189b
• Water vapor detection in the transmission spectra of HD 209458 b with the CARMENES NIR channel
• Detection of Fe and evidence for TiO in the dayside emission spectrum of WASP-33b
• Exploring the atmospheric dynamics of the extreme ultra-hot Jupiter KELT-9b using TESS photometry
• Detection of Fe I and Fe II in the atmosphere of MASCARA-2b using a cross-correlation method
• Retrieval survey of metals in six ultra-hot Jupiters: Trends in chemistry, rain-out, ionisation and atmospheric dynamics
• Hydrogen and Sodium Absorption in the Optical Transmission Spectrum of WASP-12b
• Non-local thermodynamic equilibrium effects determine the upper atmospheric temperature structure of the ultra-hot Jupiter KELT-9b
• High-resolution Transmission Spectroscopy of MASCARA-2 b with EXPRES
• Rapid escape of ultra-hot exoplanet atmospheres driven by Hydrogen Balmer absorption
• Is there NaI in the atmosphere of HD 209458b? Effect of the centre-to-limb variation and Rossiter-McLaughlin effect in transmission spectroscopy studies
• The GAPS Programme with HARPS-N at TNG XIX. Atmospheric Rossiter-McLaughlin effect and improved parameters of KELT-9b
• Cloud property trends in hot and ultra-hot giant gas planets (WASP-43b, WASP-103b, WASP-121b, HAT-P-7b, and WASP-18b)
• H$\alpha$ and He I absorption in HAT-P-32 b observed with CARMENES -- Detection of Roche lobe overflow and mass loss
• Detection of barium in the atmospheres of the ultra-hot gas giants WASP-76b and WASP-121b
• Neutral Cr and V in the atmosphere of ultra hot jupiter WASP-121 b
• The post-transit tail of WASP-107b observed at 10830A
• Evolution of atmospheric escape in close-in giant planets and their associated Ly$\alpha$ and H$\alpha$ transit predictions
• A tentative detection of He I in the atmosphere of GJ 1214b
• Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic
• High-resolution transmission spectroscopy study of ultra-hot Jupiters HAT-P-57b, KELT-17b, KELT-21b, KELT-7b, MASCARA-1b, and WASP-189b
• XUV Radiation from A-stars: Implications for Ultra-hot Jupiters
• Modelling the He I triplet absorption at 10830 Angstroms in the atmospheres of HD 189733 b and GJ 3470 b
• Detection of the hydrogen Balmer lines in the ultra-hot Jupiter WASP-33b
• TOI-2109b: An Ultrahot Gas Giant on a 16 hr Orbit
• Confirmation of Iron Emission Lines and Non-detection of TiO on the Dayside of KELT-9b with MAROON-X
• Detection of iron emission lines and a temperature inversion on the dayside of the ultra-hot Jupiter KELT-20b
• Metastable Helium Reveals an Extended Atmosphere for the Gas Giant HAT-P-18b
• High-resolution detection of neutral oxygen and non-LTE effects in the atmosphere of KELT-9b
• Mass determinations of the three mini-Neptunes transiting TOI-125
• The Mantis Network III: Expanding the limits of chemical searches within ultra hot-Jupiters. New detections of Ca I, V I, Ti I, Cr I, Ni I, Sr II, Ba II, and Tb II in KELT-9 b
• UV Exoplanet Transmission Spectral Features as Probes of Metals and Rainout
• Time-resolved rotational velocities in the upper atmosphere of WASP-33 b
• The Hubble WFC3 Emission Spectrum of the Extremely-Hot Jupiter, KELT-9b
• Atmospheric characterization of the ultra-hot Jupiter WASP-33b: Detection of Ti and V emission lines and retrieval of a broadened line profile
• Mining the Ultra-Hot Skies of HAT-P-70b: Detection of a Profusion of Neutral and Ionized Species
• Detection of CO emission lines in the dayside atmospheres of WASP-33b and WASP-189b with GIANO
• A Search for FeH in Hot-Jupiter Atmospheres with High-Dispersion Spectroscopy
• Caught in the Act: Core-powered Mass-loss Predictions for Observing Atmospheric Escape
• CRIRES+ detection of CO emissions lines and temperature inversions on the dayside of WASP-18b and WASP-76b
• Black Mirror: The impact of rotational broadening on the search for reflected light from 51 Pegasi b with high resolution spectroscopy
• A data-driven approach to constraining the atmospheric temperature structure of KELT-9b
• Revisiting the potassium feature of WASP-31b at high-resolution
• A survey of sodium absorption in ten giant exoplanets with high-resolution transmission spectroscopy
• Characterizing exoplanetary atmospheres at high resolution with SPIRou: Detection of water on HD 189733 b
• TESS Reveals a Short-period Sub-Neptune Sibling (HD 86226c) to a Known Long-period Giant Planet
• Silicon in the dayside atmospheres of two ultra-hot Jupiters
• Characterisation of the upper atmospheres of HAT-P-32 b, WASP-69 b, GJ 1214 b, and WASP-76 b through their He I triplet absorption
• The PEPSI Exoplanet Transit Survey (PETS) I: Investigating the presence of a silicate atmosphere on the super-Earth 55 Cnc e
• The MOPYS project: A survey of 70 planets in search of extended He I and H atmospheres. No evidence of enhanced evaporation in young planets
• A hydrodynamic study of the escape of metal species and excited hydrogen from the atmosphere of the hot Jupiter WASP-121b
• The potassium absorption on HD189733b and HD209458b
• Constraining planetary mass-loss rates by simulating Parker wind profiles with Cloudy
• Variable and super-sonic winds in the atmosphere of an ultra-hot giant planet
• Detection of Na in WASP-21b's lower and upper atmosphere
• Exoplanet atmospheres at high resolution through a modest-size telescope. Fe II in MASCARA-2b and KELT-9b with FIES on the Nordic Optical Telescope
• Indications for very high metallicity and absence of methane for the eccentric exo-Saturn WASP-117b
• MASCARA-4 b/bRing-1b - A retrograde hot Jupiter around the bright A3V star HD 85628
• Transmission spectroscopy of MASCARA-1b with ESPRESSO: Challenges of overlapping orbital and Doppler tracks
• LBT transmission spectroscopy of HAT-P-12b: confirmation of a cloudy atmosphere with no significant alkali features
• The stable climate of KELT-9b
• The obliquity and atmosphere of the ultra-hot Jupiter TOI-1431b (MASCARA-5b): A misaligned orbit and no signs of atomic ormolecular absorptions
• Modeling H$\alpha$ and He 10830 transmission spectrum of WASP-52b
• Transmission spectroscopy of the ultra-hot Jupiter MASCARA-4 b: Disentangling the hydrostatic and exospheric regimes of ultra-hot Jupiters
• Transmission spectroscopy of the lowest-density gas giant: metals and a potential extended outflow in HAT-P-67b
• Stellar impact on disequilibrium chemistry and on observed spectra of hot Jupiter atmospheres
• Detection of Paschen $\beta$ absorption in the atmosphere of KELT-9 b: A new window into the atmospheres of ultra-hot Jupiters
• Dynamics and Clouds in Planetary Atmospheres from Telescopic Observations
• Discriminating between hazy and clear hot-Jupiter atmospheres with CARMENES
• HIP 33609 b: An Eccentric Brown Dwarf Transiting a V=7.3 Rapidly Rotating B-Star
• Obliquity measurement and atmospheric characterization of the WASP-74 planetary system
• High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts
• KELT-9 as an eclipsing double-lined spectroscopic binary: a unique and self-consistent solution to the system
• The atmosphere of WASP-17b: Optical high-resolution transmission spectroscopy
• The Maximum Mass-Loss Efficiency for a Photoionization-Driven Isothermal Parker Wind
• The PEPSI Exoplanet Transit Survey. III: The detection of FeI, CrI and TiI in the atmosphere of MASCARA-1 b through high-resolution emission spectroscopy
• Remote sensing of exoplanetary atmospheres with ground-based high-resolution near-infrared spectroscopy
• Characterization of exoplanetary atmospheres with SLOPpy
• Hot planets around cool stars -- two short-period mini-Neptunes transiting the late K-dwarf TOI-1260
• Non-Local Thermodynamic Equilibrium Transmission Spectrum Modelling of HD209458b
• The GAPS programme at TNG: TBD. Studies of atmospheric FeII winds in ultra-hot Jupiters KELT-9b and KELT-20b using HARPS-N spectrograph
• Non-detection of Helium in the Hot Jupiter WASP-48b
• An efficient Monte Carlo model for the slowing down of photoelectrons. Application to H-$\alpha$ in exoplanet atmospheres
• The GAPS programme at TNG LX Atmospheric characterisation of KELT-9 b via single-line analysis: Detection of six H I Balmer lines, Na I, Ca I, Ca II, Fe I, Fe II, Mg I, Ti II, Sc II, and Cr II
• Atmosphere escape inferred from modelling the H$\alpha$ transmission spectrum of WASP-121b
• Multi-epoch detections of the extended atmosphere and transmission spectra of KELT-9b with a 1.5 m telescope
• Probing the atmosphere of HD189733b with the Na I and K I lines
• Detection of rubidium and samarium in the atmosphere of the ultra-hot Jupiter MASCARA-4b
• The GAPS Programme at TNG. XXX: Characterization of the low-density gas giant HAT-P-67 b with GIARPS
• HD 56414 b: A Warm Neptune Transiting an A-type Star
• Instrumentation prospects for rocky exoplanet atmospheres studies with high resolution spectroscopy
• HORuS transmission spectroscopy and revised planetary parameters of KELT-7b
• Probing Na in giant exoplanets with ESPRESSO and 3D NLTE stellar spectra
• Extreme winds on the emerging dayside of an ultrahot Jupiter
• Hydride ion continuum hides absorption signatures in the NIRPS near-infrared transmission spectrum of the ultra-hot gas giant WASP-189b
• Retrieving day- and nightside atmospheric properties of the ultra-hot Jupiter TOI-2109b. Detection of Fe and CO emission lines and evidence for inefficient heat transport
• Colorado Ultraviolet Transit Experiment Data Simulator
• The escape of hydrogen-rich atmosphere of exoplanet: Mass loss rates and the absorptions of stellar Lyman $\alpha$
• Following the TraCS of exoplanets with Pan-Planets: Wendelstein-1b and Wendelstein-2b
• KELT-9 and its ultra-hot Jupiter: stellar parameters, composition, and planetary pollution
• NLTE atmospheric modelling of the ultra-hot Jupiter WASP-178b and comparison with UV and optical observations
• Experimental Investigation of the Photochemical Production of Hydrocarbons in Warm Gas Giant Exoplanet Atmospheres
• The ESPRESSO transmission spectrum of HD189733b : Extracting the planetary sodium and lithium signatures amid stellar contamination
• Modelling helium in exoplanet atmospheres. A revised network with photoelectron-driven processes
• The effects of stellar gravity darkening on high-resolution transmission spectra
• Assessing the residual biases in high-resolution transit absorption spectra correction
• Atmospheric composition of WASP-85Ab with ESPRESSO/VLT observations
• Is the high-energy environment of K2-18b special?
• PEPSI's non-detection of escaping hydrogen and metal lines adds to the enigma of WASP-12 b
• Probing the geological setting of exoplanets through atmospheric analysis: using Mars as a test case
• Thermal emission spectra of the ultra-hot Jupiter WASP-33 b
• Revisiting the atmosphere of HAT-P-70b with CARMENES high-resolution transmission spectroscopy
• TOI-1518b: A Misaligned Ultra-hot Jupiter with Iron in its Atmosphere
• CARMENES detection of the CaII infrared triplet and possible evidence of HeI in the atmosphere of WASP-76b
• A search for transits among the δ Scuti variables in Kepler