JWST-TST High Contrast: Living on the Wedge, or, NIRCam Bar Coronagraphy Reveals CO${}_2$ in the HR 8799 and 51 Eri Exoplanets' Atmospheres

Abstract

High-contrast observations with JWST can reveal key composition and vertical mixing dependent absorption features in the spectra of directly imaged planets across the 3-5 $\mu$m wavelength range. We present novel coronagraphic images of the HR 8799 and 51 Eri planetary systems using the NIRCam Long Wavelength Bar in an offset "narrow" position. These observations have revealed the four known gas giant planets encircling HR 8799, even at spatial separations challenging for a 6.5 m telescope in the mid-infrared, including the first ever detection of HR 8799 e at 4.6 $\mu$m. The chosen filters constrain the strength of CO, CH4, and CO2 absorption in each planet's photosphere. The planets display a diversity of 3-5 $\mu$m colors that could be due to differences in composition and ultimately be used to trace their formation history. They also show stronger CO2 absorption than expected from solar metallicity models, indicating that they are metal enriched. We detected 51 Eri b at 4.1 $\mu$m and not at longer wavelengths, which, given the planet's temperature, is indicative of out-of-equilibrium carbon chemistry and an enhanced metallicity. Updated orbits fit to the new measurement of 51 Eri b validate previous studies that find a preference for high eccentricities ($e=0.57_{-0.09}^{+0.03}$), which likely indicates some dynamical processing in the system's past. These results present an exciting opportunity to model the atmospheres and formation histories of these planets in more detail in the near future, and are complementary to future higher-resolution, continuum-subtracted JWST spectroscopy.

arXiv commentPublished in AJ, associated with press release https://webbtelescope.org/contents/news-releases/2025/news-2025-114. 32 pages, 16 figures, 4 appendices, 3 tables. v2 corrects mJy to uJy in Table 2 header & caption

References in corpus (125)

• emcee: The MCMC Hammer
• Gaia Data Release 3: Summary of the content and survey properties
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• Multimodal nested sampling: an efficient and robust alternative to MCMC methods for astronomical data analysis
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• The effects of snowlines on C/O in planetary atmospheres
• Importance Nested Sampling and the MultiNest Algorithm
• Images of a fourth planet orbiting HR 8799
• Detection and Characterization of Exoplanets and Disks using Projections on Karhunen-Loeve Eigenimages
• A Giant Planet Candidate near a Young Brown Dwarf
• A probable giant planet imaged in the Beta Pictoris disk
• Discovery and spectroscopy of the young Jovian planet 51 Eri b with the Gemini Planet Imager
• BANYAN. XI. The BANYAN $\Sigma$ multivariate Bayesian algorithm to identify members of young associations within 150 pc
• A self-consistent, absolute isochronal age scale for young moving groups in the solar neighbourhood
• Origins of Eccentric Extrasolar Planets: Testing the Planet-Planet Scattering Model
• The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics From 10-100 AU
• The Science Performance of JWST as Characterized in Commissioning
• Detection of Carbon Monoxide and Water Absorption Lines in an Exoplanet Atmosphere
• Fundamental limitations of high contrast imaging set by small sample statistics
• Spectral and Photometric Diagnostics of Giant Planet Formation Scenarios
• Imaging Extrasolar Giant Planets
• Clouds and Chemistry in the Atmosphere of Extrasolar Planet HR8799b
• Early Release Science of the exoplanet WASP-39b with JWST NIRSpec PRISM
• Dynamic temperature selection for parallel-tempering in Markov chain Monte Carlo simulations
• A Combined Subaru/VLT/MMT 1--5 Micron Study of Planets Orbiting HR 8799: Implications for Atmospheric Properties, Masses, and Formation
• The Hipparcos-Gaia Catalog of Accelerations: Gaia EDR3 Edition
• Spitzer IRS Spectroscopy of IRAS-Discovered Debris Disks
• Masses, Radii, and Cloud Properties of the HR 8799 Planets
• The Tucana/Horologium, Columba, AB Doradus, and Argus Associations: New Members and Dusty Debris Disks
• Direct Imaging of a Cold Jovian Exoplanet in Orbit around the Sun-like Star GJ 504
• Population Properties of Brown Dwarf Analogs to Exoplanets
• The Debris Disk Around HR 8799
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• The SPHERE infrared survey for exoplanets (SHINE). III. The demographics of young giant exoplanets below 300 au with SPHERE
• Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e
• A Coronagraph with a Band-Limited Mask for Finding Terrestrial Planets
• Near-Infrared Spectroscopy of the Extrasolar Planet HR 8799 b
• Early Release Science of the exoplanet WASP-39b with JWST NIRCam
• Simultaneous Detection of Water, Methane and Carbon Monoxide in the Atmosphere of Exoplanet HR8799b
• A self-consistent cloud model for brown dwarfs and young giant exoplanets: comparison with photometric and spectroscopic observations
• The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 Micron Spectrum of the Planetary-Mass Companion VHS 1256-1257 b
• How drifting and evaporating pebbles shape giant planets I: Heavy element content and atmospheric C/O
• The Complete transmission spectrum of WASP-39b with a precise water constraint
• Detection and Characterization of Exoplanets using Projections on Karhunen-Loeve Eigenimages: Forward Modeling
• Spectral and atmospheric characterization of 51 Eridani b using VLT/SPHERE
• HAT-P-20b--HAT-P-23b: Four Massive Transiting Extrasolar Planets
• orbitize!: A Comprehensive Orbit-fitting Software Package for the High-contrast Imaging Community
• First direct detection of an exoplanet by optical interferometry; Astrometry and K-band spectroscopy of HR8799 e
• First light of the VLT planet finder SPHERE. IV. Physical and chemical properties of the planets around HR8799
• Stellar encounters as the origin of distant solar system objects in highly eccentric orbits
• Directly Imaged L-T Transition Exoplanets in the Mid-Infrared
• Dynamical Constraints on the HR 8799 Planets with GPI
• HST/NICMOS detection of HR 8799 b in 1998
• MIRACLES: atmospheric characterization of directly imaged planets and substellar companions at 4-5 $\mu$m. I. Photometric analysis of $\beta$ Pic b, HIP 65426 b, PZ Tel B and HD 206893 B
• M-band Imaging of the HR 8799 Planetary System Using an Innovative LOCI-based Background Subtraction Technique
• Characterizing 51 Eri b from 1-5 $\mu$m: a partly-cloudy exoplanet
• Spitzer/MIPS Observations of Stars in the Beta Pictoris Moving Group
• Resolved Imaging of the HR 8799 Debris Disk with Herschel
• New Grids of Pure-Hydrogen White-Dwarf NLTE Model Atmospheres \newline and the HST/STIS Flux Calibration
• Stellar population models in the UV: I. Characterisation of the New Generation Stellar Library
• Chasing Shadows: Rotation of the Azimuthal Asymmetry in the TW Hya Disk
• The Orbit and Transit Prospects for $\beta$ Pictoris b constrained with One Milliarcsecond Astrometry
• Thermal Infrared MMTAO Observations of the HR 8799 Planetary System
• Resolved Submillimeter Observations of the HR 8799 and HD 107146 Debris Disks
• The CHARA Array Angular Diameter of HR 8799 Favors Planetary Masses for Its Imaged Companions
• Photolytic Hazes in the Atmosphere of 51 Eri b
• How drifting and evaporating pebbles shape giant planets II: Volatiles and refractories in atmospheres
• Gas and dust in the Beta Pictoris Moving Group as seen by the Herschel Space Observatory
• The mass of Beta Pictoris c from Beta Pictoris b orbital motion
• Keck/NIRC2 $L$'-Band Imaging of Jovian-Mass Accreting Protoplanets around PDS 70
• Resolving the Planetesimal Belt of HR 8799 with ALMA
• AF Lep b: the lowest mass planet detected coupling astrometric and direct imaging data
• Radial Velocity Measurements of HR 8799 b and c with Medium Resolution Spectroscopy
• AKARI Observations of Brown Dwarfs. III. CO, CO2 and CH4 Fundamental Bands and Physical Parameters
• Direct imaging discovery of a super-Jovian around the young Sun-like star AF Leporis
• Astrometric Confirmation and Preliminary Orbital Parameters of the Young Exoplanet 51 Eridani b with the Gemini Planet Imager
• Astrometric Accelerations as Dynamical Beacons: A Giant Planet Imaged Inside the Debris Disk of the Young Star AF Lep
• The LEECH Exoplanet Imaging Survey: Limits on Planet Occurrence Rates Under Conservative Assumptions
• LBT observations of the HR 8799 planetary system: First detection of HR8799e in H band
• A Clear View of a Cloudy Brown Dwarf Companion from High-Resolution Spectroscopy
• Locating the planetesimals belts in the multiple-planet systems HD 128311, HD 202206, HD 82943 and HR 8799
• Age determination of the HR8799 planetary system using asteroseismology
• Deep Thermal Infrared Imaging of HR 8799 bcde: New Atmospheric Constraints and Limits on a Fifth Planet
• The Measurement, Treatment, and Impact of Spectral Covariance and Bayesian Priors in Integral-Field Spectroscopy of Exoplanets
• GPI spectra of HR 8799 c, d, and e from 1.5 to 2.4$\mu$m with KLIP Forward Modeling
• Determination of the inclination of the multi-planet hosting star HR8799 using asteroseismology
• A temperate super-Jupiter imaged with JWST in the mid-infrared
• The LEECH Exoplanet Imaging Survey. Further constraints on the planet architecture of the HR 8799 system
• On the Radii of Brown Dwarfs Measured with AKARI Near-Infrared Spectroscopy
• Solar System Analogs Around IRAS-Discovered Debris Disks
• The Nancy Grace Roman Space Telescope Coronagraph Instrument (CGI) Technology Demonstration
• H band Image of a Planetary Companion around HR 8799 in 2002
• Four-of-a-kind? Comprehensive atmospheric characterisation of the HR 8799 planets with VLTI/GRAVITY
• A detailed characterization of HR 8799's debris disk with ALMA in Band 7
• The Second Discovery from the COol Companions ON Ultrawide orbiTS (COCONUTS) Program: A Cold Wide-Orbit Exoplanet around a Young Field M Dwarf at 10.9 pc
• Hint of curvature in the orbital motion of the exoplanet 51 Eridani b using 3 years of VLT/SPHERE monitoring
• On the origin of the wide-orbit circumbinary giant planet HD 106906: A dynamical scenario and its impact on the disk
• The Scattered Disc of HR 8799
• On the Chemical Abundance of HR 8799 and the Planet c
• Retrieving C and O Abundance of HR 8799 c by Combining High- and Low-Resolution Data
• Direct imaging of sub-Jupiter mass exoplanets with James Webb Space Telescope coronagraphy
• Orbital and dynamical analysis of the system around HR 8799. New astrometric epochs from VLT/SPHERE and LBT/LUCI
• A High-Contrast Search for Variability in HR 8799bc with VLT-SPHERE
• Retrieval study of cool, directly imaged exoplanet 51 Eri b
• Revisiting the atmosphere of the exoplanet 51 Eridani b with VLT/SPHERE
• VLT/NACO astrometry of the HR8799 planetary system. L'-band observations of the three outer planets
• Imaging detection of the inner dust belt and the four exoplanets in the HR8799 system with JWST's MIRI coronagraph
• Enriching inner discs and giant planets with heavy elements
• Limits on the Mass and Initial Entropy of 51 Eri b from Gaia EDR3 Astrometry
• On the radial distribution of giant exoplanets at Solar System scales
• Atmospheric Monitoring and Precise Spectroscopy of the HR 8799 Planets with SCExAO/CHARIS
• An updated visual orbit of the directly-imaged exoplanet 51 Eridani b and prospects for a dynamical mass measurement with Gaia
• End-to-end numerical modeling of the Roman Space Telescope coronagraph
• Deep orbital search for additional planets in the HR 8799 system
• MOST light-curve analysis of the gamma Dor pulsator HR 8799, showing resonances and amplitude variations
• First Observations of the Brown Dwarf HD 19467 B with JWST
• Precise dynamical masses of new directly imaged companions from combining relative astrometry, radial velocities, and Hipparcos-Gaia eDR3 accelerations
• JWST-TST High Contrast: JWST/NIRCam observations of the young giant planet $\beta$ Pic b
• The Giant Accreting Protoplanet Survey (GAPlanetS): Optimization Techniques for Robust Detections of Protoplanets
• New constraints on the HR 8799 planetary system from mid-infrared direct imaging
• A catalogue of dual-field interferometric binary calibrators
• The infrared colors of 51 Eridani b: micrometereoid dust or chemical disequilibrium?
• Measuring the Stellar and Planetary Properties of the 51 Eridani System
• Searching for magnetic fields in pulsating A-type stars: the discovery of a strong field in the probable delta Sct star HD340577 and a null result for the gamma Dor star HR8799

Cited by in corpus (7)

• Jupiter-like uniform metal enrichment in a system of multiple giant exoplanets
• The compositions of the HR 8799 planets reflect accretion of both solids and metal-enriched gas
• Direct Spectroscopy of 51 Eridani b with JWST NIRSpec
• Measurements and predictions of H2 pressure-broadening coefficients of CO2 absorption lines for exoplanet atmosphere studies
• Direct Imaging Discovery of Giant Exoplanet $\beta$ Pictoris d: A Decade-Long Game of Hide-and-Seek
• Direct Images of CO2 Absorption in the Atmosphere of a Super-Jupiter: Enhanced Metallicity Suggestive of Formation in a Disk
• Imaging exoplanets below the telescope stability limit