TESS hunt for young and maturing exoplanets (THYME). V. A sub-neptune transiting a young star in a newly discovered 250myr association

Benjamin M. Tofflemire, Aaron C. Rizzuto, Elisabeth R. Newton, Adam L. Kraus, Andrew W. Mann, Andrew Vanderburg, Tyler Nelson, Keith Hawkins, Mackenna L. Wood, George Zhou, Samuel N. Quinn, Steve B. Howell, Karen A. Collins, Richard P. Schwarz, Keivan G. Stassun, Luke G. Bouma, Zahra Essack, Hugh Osborn, Patricia T. Boyd, Gábor FűrészAna Glidden, Joseph D. Twicken, Bill Wohler, Brian McLean, George R. Ricker, Roland Vanderspek, David W. Latham, S. Seager, Joshua N. Winn, Jon M. Jenkins

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


The detection and characterization of young planetary systems offer a direct path to study the processes that shape planet evolution. We report on the discovery of a sub-Neptune-sized planet orbiting the young star HD 110082 (TOI-1098). Transit events we initially detected during TESS Cycle 1 are validated with time-series photometry from Spitzer. High-contrast imaging and high-resolution, optical spectra are also obtained to characterize the stellar host and confirm the planetary nature of the transits. The host star is a late-F dwarf (Må = 1.2Me) with a low-mass, M dwarf binary companion (Må = 0.26Me) separated by nearly one arcminute (∼6200 au). Based on its rapid rotation and Lithium absorption, HD 110082 is young, but is not a member of any known group of young stars (despite proximity to the Octans association). To measure the age of the system, we search for coeval, phase-space neighbors and compile a sample of candidate siblings to compare with the empirical sequences of young clusters and to apply quantitative age-dating techniques. In doing so, we find that HD 110082 resides in a new young stellar association we designate MELANGE-1, with an age of 250-+7050 Myr. Jointly modeling the TESS and Spitzer light curves, we measure a planetary orbital period of 10.1827 days and radius of Rp = 3.2 ± 0.1R+. HD 110082 b’s radius falls in the largest 12% of field-age systems with similar host-star mass and orbital period. This finding supports previous studies indicating that young planets have larger radii than their field-age counterparts.

Original languageEnglish (US)
Article number171
JournalAstronomical Journal
Issue number4
StatePublished - Apr 1 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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