Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of $\alpha$ Cen A. I. Observations, Orbital and Physical Properties, and Exozodi Upper Limits

Abstract

We report on coronagraphic observations of the nearest solar-type star, $\alpha$ Cen A, using the MIRI instrument on the James Webb Space Telescope. With three epochs of observation (August 2024, February 2025, and April 2025), we achieve a sensitivity sufficient to detect $T_{\mathrm{eff}}\approx$ 225-250 K (1-1.2 $R_{\mathrm{Jup}}$) planets between 1"-2" and exozodiacal dust emission at the level of $>$5-8$\times$ the brightness of our own zodiacal cloud. The lack of exozodiacal dust emission sets an unprecedented limit of a few times the brightness of our own zodiacal cloud$-$a factor of $\gtrsim$10 more sensitive than measured toward any other stellar system to date. In August 2024, we detected a F${}_{\nu }$(15.5 $\mu$m) = 3.5 mJy point source, called $S1$, at a separation of 1.5" from $\alpha$ Cen A. Because the August 2024 epoch had only one successful observation at a single roll angle, it is not possible to unambiguously confirm $S1$ as a bona fide planet. Our analysis confirms that $S1$ is neither a background nor a foreground object. $S1$ is not recovered in the February and April 2025 epochs. However, if $S1$ is the counterpart of the object, $C1$, seen by the VLT/NEAR program in 2019, we find that there is a 52% chance that the $S1+C1$ candidate was missed in both follow-up JWST/MIRI observations due to orbital motion. Incorporating constraints from the non-detections, we obtain families of dynamically stable orbits for $S1+C1$ with periods between 2-3 years. These suggest that the planet candidate is on an eccentric ($e\approx 0.4$) orbit significantly inclined with respect to $\alpha$ Cen AB orbital plane ($i_{\mathrm{mutual}}\approx 50^{\circ }$, or $\approx 130^{\circ }$). Based on the photometry and orbital properties, the planet candidate could have a temperature of 225 K, a radius of $\approx$1-1.1 $R_{\mathrm{Jup}}$ and a mass between 90-150 $M_{\mathrm{Earth}}$, consistent with RV limits.

arXiv commentAccepted to ApJL. 34 pages, 22 figures, 10 tables

References in corpus (66)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• emcee: The MCMC Hammer
• The Gaia mission
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• REBOUND: An open-source multi-purpose N-body code for collisional dynamics
• Spectral Energy Distributions of Hard X-ray selected AGNs in the XMDS Survey
• The Eccentric Kozai-Lidov Effect and Its Applications
• The Infrared Astronomical Mission AKARI
• Detection and Characterization of Exoplanets and Disks using Projections on Karhunen-Loeve Eigenimages
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• The COBE Diffuse Infrared Background Experiment Search for the Cosmic Infrared Background: II. Model of the Interplanetary Dust Cloud
• The Science Performance of JWST as Characterized in Commissioning
• Fundamental limitations of high contrast imaging set by small sample statistics
• Debris disks in main sequence binary systems
• A new set of atmosphere and evolution models for cool T-Y brown dwarfs and giant exoplanets
• The Impact of Stellar Multiplicity on Planetary Systems, I.: The Ruinous Influence of Close Binary Companions
• Validation of Kepler's Multiple Planet Candidates. II: Refined Statistical Framework and Descriptions of Systems of Special Interest
• The Mid-Infrared Instrument for JWST, II: Design and Build
• The Insignificance of P-R Drag in Detectable Extrasolar Planetesimal Belts
• Water Clouds in Y Dwarfs and Exoplanets
• Exoplanet Reflected Light Spectroscopy with PICASO
• orbitize!: A Comprehensive Orbit-fitting Software Package for the High-contrast Imaging Community
• Planck intermediate results. XXIX. All-sky dust modelling with Planck, IRAS, and WISE observations
• Debris disk size distributions: steady state collisional evolution with P-R drag and other loss processes
• Planets and IR Excesses: Preliminary Results from a Spitzer/MIPS Survey of Solar-Type Stars
• Impact of Binary Stars on Planet Statistics -- I. Planet Occurrence Rates, Trends with Stellar Mass, and Wide Companions to Hot Jupiter Hosts
• PICASO 3.0: A One-Dimensional Climate Model for Giant Planets and Brown Dwarfs
• The HOSTS survey for exozodiacal dust: Observational results from the complete survey
• Orbits for the Impatient: A Bayesian Rejection Sampling Method for Quickly Fitting the Orbits of Long-Period Exoplanets
• Ultra-high-precision velocity measurements of oscillations in alpha Cen A
• The Anglo-Australian Planet Search XXIV: The Frequency of Jupiter Analogs
• The Mid-Infrared Instrument for the James Webb Space Telescope, VII: The MIRI Detectors
• The Sonora Substellar Atmosphere Models. IV. Elf Owl: Atmospheric Mixing and Chemical Disequilibrium with Varying Metallicity and C/O Ratios
• The Mid-Infrared Instrument for the James Webb Space Telescope, V: Predicted Performance of the MIRI Coronagraphs
• Evidence for a high mutual inclination between the cold Jupiter and transiting super Earth orbiting $\pi$ Men
• The radii and limb darkenings of Alpha Centauri A and B - Interferometric measurements with VLTI/PIONIER
• The HOSTS survey - Exozodiacal dust measurements for 30 stars
• Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry
• Close stellar conjunctions of alpha Centauri A and B until 2050 - An mK = 7.8 star may enter the Einstein ring of alpha Cen A in 2028
• Long-Term Stability of Planets in the $\alpha$ Centauri System
• Imaging low-mass planets within the habitable zone of α Centauri
• A statistically significant lack of debris discs in medium separation binary systems
• High order symplectic integrators for planetary dynamics and their implementation in REBOUND
• Orbital Architectures of Planet-Hosting Binaries II. Low Mutual Inclinations Between Planetary and Stellar Orbits
• Kuiper belt structure around nearby super-Earth host stars
• Planet Detectability in the Alpha Centauri System
• Long-term photometry and periods for 261 nearby pulsating M giants
• Precision Millimeter Astrometry of the $\alpha$ Centauri AB System
• Long-Term Stability of Tightly Packed Multi-Planet Systems in Prograde, Coplanar, Circumstellar Orbits within the $\alpha$ Centauri AB System
• Dust size and spatial distributions in debris discs: predictions for exozodiacal dust dragged in from an exo-Kuiper belt
• Searching for Planets Orbiting Alpha Centauri A with the James Webb Space Telescope
• The Sonora Substellar Atmosphere Models. V: A Correction to the Disequilibrium Abundance of CO${}_2$ for Sonora Elf Owl
• Revising Properties of Planet-Host Binary Systems. IV. The Radius Distribution of Small Planets in Binary Star Systems is Dependent on Stellar Separation
• Long-Term Stability of Planets in the $\alpha$ Centauri System, II: Forced Eccentricities
• How dusty is alpha Centauri? Excess or non-excess over the infrared photospheres of main-sequence stars
• Optimal Fitting and Debiasing for Detectors Read Out Up-the-Ramp
• Searching for Saturn's Dust Swarm: Limits on the size distribution of Irregular Satellites from km to micron sizes
• Extremely Inclined Orbit of S-type Planet $\gamma$ Cep Ab Induced by Eccentric Kozai-Lidov Mechanism
• A PR drag origin for the Fomalhaut disk's pervasive inner dust: constraints on collisional strengths, icy composition, and embedded planets
• Chasing extreme planetary architectures: I- HD196885Ab, a super-Jupiter dancing with two stars?
• Dust extinction map of the Galactic plane based on the VVV survey data
• Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of $\alpha$ Cen A. II. Binary Star Modeling, Planet and Exozodi Search, and Sensitivity Analysis
• A Year of Wavefront Sensing with JWST in Flight: Cycle 1 Telescope Monitoring and Maintenance Summary
• Debris discs in binaries: morphology and photometric signatures

Cited by in corpus (5)

• Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of $\alpha$ Cen A. II. Binary Star Modeling, Planet and Exozodi Search, and Sensitivity Analysis
• PICASO 4.0: Clouds and Photochemistry in Climate Models of Brown Dwarfs and Exoplanets
• Astrometric exomoon detection by means of optical interferometry
• SPORES-HWO. II. Companion Mass Limits and Updated Planet Properties for 120 Future Exoplanet Imaging Targets from 35 yr of Precise Doppler Monitoring
• Searching for Planets around Altair with JWST/NIRcam