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

Abstract

Copyright and License

© 2025. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

The STScI support staff provided invaluable assistance in the planning and execution of this program. In particular, we thank George Chapman and the FGS team for their dedicated work in finding and vetting guide stars for this program and Wilson Joy Skipper and the short- and long-range planning teams for their contributions to this challenging observational program. The STScI’s Director’s Office provided strong support for this program, from its initial selection as a high-risk, high-reward project, granting time to conduct test observations needed to validate the TA strategy, to the execution of the follow-up DDT programs. We gratefully acknowledge the ALMA Director’s Discretionary Time program. In particular we wish to thank Richard Simon, Bill Dent, Brian Mason, Erica Keller, and Ilsang Yoon for their assistance in completing these critical observations in a timely manner. Dan Sirbu provided constructive comments on an earlier version of this manuscript. We thank the referee for a prompt report and helpful comments that improved this manuscript.

The specific observations analyzed can be accessed via doi: 10.17909/v8nv-vx17 for the 2024 August observations, doi: 10.17909/cb0x-rn85 for the 2025 February observations, and doi: 10.17909/3z9q-9f65 for the 2025 April observations. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support to MAST for these data is provided by the NASA Office of Space Science via grant NAG5-7584 and by other grants and contracts. This research has made use of NASA’s Astrophysics Data System. Portions of this research were conducted with the advanced computing resources provided by Texas A&M High Performance Research Computing that was supported in part by the National Science Foundation (NSF) under grant #2232895. This Letter makes use of the following ALMA data: ADS/JAO.ALMA#2022.A.00017.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This publication makes use of VOSA, developed under the Spanish Virtual Observatory (https://svo.cab.inta-csic.es) project funded by MCIN/AEI/10.13039/501100011033/ through grant PID2020-112949GB-I00. VOSA has been partially updated by using funding from the European Union’s Horizon 2020 Research and Innovation Programme, under grant Agreement #776403 (EXOPLANETS-A). This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.

This material is based on work supported by the National Science Foundation Graduate Research Fellowship under grant No. 2139433. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). Program PID#1618, #6797, and #9252 are supported through contracts JWST-GO-01618.001, JWST-GO-06797.001, and JWST-GO-09252.001, respectively. Research done at NASA’s Ames Research Center was supported by the NASA Astrophysics Division’s Internal Scientist Funding Model (ISFM) program. This project is cofunded by the European Union (ERC, ESCAPE, project No 101044152). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them.

Contributions

C.A.B. and A.S. led the writing and submission of this manuscript. C.A.B. developed the observational strategy and sequences in conjunction with D.H., J.A., and M.R. R.A. and E.F. executed and reduced the ALMA data. P.K. developed the detailed astrometric solution used for α Cen AB. A.S. led the postprocessing of the MIRI observations with the assistance of D.M., W.B., L.P., A.B., and J.L.-S. Analysis of the possible orbits of the α Cen A candidate was conducted by A.S., K.W., B.Q., and J.L. Photometric modeling of the α Cen A candidate was carried out by A.S. with the assistance of M.Z. and R.H. Custom atmospheric models were generated by J.M. and P.T. Dust emission models for the zodiacal cloud and an exoplanet ring system were developed by M.S., M.W., and C.A.B. Analysis of the extended emission was carried out by N.G. and E.C. All authors assisted with the preparation of the original JWST proposal and the manuscript.

Facilities

JWST - James Webb Space Telescope (MIRI), ALMA - Atacama Large Millimeter Array, Gaia - .

Software References

astropy Astropy Collaboration et al. 2022), emcee (D. Foreman-Mackey et al. 2013), jwst (H. Bushouse et al. 2022), multinest F. Feroz et al. 2009), NIRCoS (J. Kammerer et al. 2022), pyNRC (J. Leisenring 2025, in preparation), pysynphot (STScI Development Team 2013), spaceKLIP (J. Kammerer et al. 2022), matplotlib (J. D. Hunter 2007), numpy (C. R. Harris et al. 2020), scipy (P. Virtanen et al. 2020), STPSF (M. D. Perrin et al. 2014), webbpsf_ext (J. Leisenring 2025, in preparation).