Exoplanets & Exomoons

TESS Hunt For Young And Maturing Exoplanets (THYME) XI: An Earth-sized Planet Orbiting a Nearby, Solar-like Host in the 400Myr Ursa Major Moving Group

By Keith Cowing
Status Report
January 14, 2024
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TESS Hunt For Young And Maturing Exoplanets (THYME) XI: An Earth-sized Planet Orbiting a Nearby, Solar-like Host in the 400Myr Ursa Major Moving Group
The top panel shows the unflattened TESS light curve of HD 63433. The middle panel shows the flattened light curve with our three best-fit transit models for planets b, c, and d, as determined by our edmcmc outputs. The colors of these models correspond to each of the three planets as shown in the bottom panels, which depict the phase-folded light curves for each HD 63433 planet with binned data (red points) plotted over our best-fit models. — astro-ph.EP

Young terrestrial worlds are critical test beds to constrain prevailing theories of planetary formation and evolution. We present the discovery of HD 63433d – a nearby (22pc), Earth-sized planet transiting a young sunlike star (TOI-1726, HD 63433). HD 63433d is the third planet detected in this multiplanet system.

The kinematic, rotational, and abundance properties of the host star indicate that it belongs to the young (414 ± 23 Myr) Ursa Major moving group, whose membership we update using new data from Gaia DR3 and TESS. Our transit analysis of the TESS light curves indicates that HD 63433 d has a radius of 1.1 R⊕ and closely orbits its host star with a period of 4.2 days.

To date, HD 63433 d is the smallest confirmed exoplanet with an age less than 500 Myr, and the nearest young Earth-sized planet. Furthermore, the apparent brightness of the stellar host (V ≈ 6.9 mag) makes this transiting multiplanet system favorable to further investigations, including spectroscopic follow-up to probe atmospheric loss in a young Earth-sized world.

Benjamin K. Capistrant, Melinda Soares-Furtado, Andrew Vanderburg, Alyssa Jankowski, Andrew W. Mann, Gabrielle Ross, Gregor Srdoc, Natalie R. Hinkel, Juliette Becker, Christian Magliano, Mary Anne Limbach, Alexander P. Stephan, Andrew C. Nine, Benjamin M. Tofflemire, Adam L. Kraus, Steven Giacalone, Joshua N. Winn, Allyson Bieryla, Luke G. Bouma, David R. Ciardi, Karen A. Collins, Giovanni Covone, Zoë L. de Beurs, Chelsea X. Huang, Samuel N. Quinn, Sara Seager, Roland K. Vanderspek, Jon M. Jenkins, Laura Kreidberg, David W. Latham, Avi Shporer, Joseph D. Twicken, Bill Wohler, Ricardo Yarza, Carl Ziegler

Comments: 24 pages, 7 figures, 6 tables. Accepted for publication in AJ. The first two authors contributed equally to the manuscript
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2401.04785 [astro-ph.EP] (or arXiv:2401.04785v1 [astro-ph.EP] for this version)
Submission history
From: Andrew Vanderburg
[v1] Tue, 9 Jan 2024 19:17:46 UTC (4,936 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻