TESS Hunt for Young and Maturing Exoplanets (THYME): A Planet in the 45 Myr Tucana-Horologium Association

Elisabeth R. Newton, Andrew W. Mann, Benjamin M. Tofflemire, Logan Pearce, Aaron C. Rizzuto, Andrew Vanderburg, Raquel A. Martinez, Jason J. Wang, Jean Baptiste Ruffio, Adam L. Kraus, Marshall C. Johnson, Pa Chia Thao, MacKenna L. Wood, Rayna Rampalli, Eric L. Nielsen, Karen A. Collins, Diana Dragomir, Coel Hellier, D. R. Anderson, Thomas BarclayCarolyn Brown, Gregory Feiden, Rhodes Hart, Giovanni Isopi, John F. Kielkopf, Franco Mallia, Peter Nelson, Joseph E. Rodriguez, Chris Stockdale, Ian A. Waite, Duncan J. Wright, Jack J. Lissauer, George R. Ricker, Roland Vanderspek, David W. Latham, S. Seager, Joshua N. Winn, Jon M. Jenkins, Luke G. Bouma, Christopher J. Burke, Misty Davies, Michael Fausnaugh, Jie Li, Robert L. Morris, Koji Mukai, Joel Villaseñor, Steven Villeneuva, Robert J. De Rosa, Bruce MacIntosh, Matthew W. Mengel, Jack Okumura, Robert A. Wittenmyer

Research output: Contribution to journalArticlepeer-review

109 Scopus citations


Young exoplanets are snapshots of the planetary evolution process. Planets that orbit stars in young associations are particularly important because the age of the planetary system is well constrained. We present the discovery of a transiting planet larger than Neptune but smaller than Saturn in the 45 Myr Tucana-Horologium young moving group. The host star is a visual binary, and our follow-up observations demonstrate that the planet orbits the G6V primary component, DS Tuc A (HD 222259A, TIC 410214986). We first identified transits using photometry from the Transiting Exoplanet Survey Satellite (TESS; alerted as TOI 200.01). We validated the planet and improved the stellar parameters using a suite of new and archival data, including spectra from Southern Astrophysical Research/Goodman, South African Extremely Large Telescope/High Resolution Spectrograph and Las Cumbres Observatories/Network of Robotic Echelle Spectrographs; transit photometry from Spitzer; and deep adaptive optics imaging from Gemini/Gemini Planet Imager. No additional stellar or planetary signals are seen in the data. We measured the planetary parameters by simultaneously modeling the photometry with a transit model and a Gaussian process to account for stellar variability. We determined that the planetary radius is 5.70 ± 0.17 R and that the orbital period is 8.1 days. The inclination angles of the host star's spin axis, the planet's orbital axis, and the visual binary's orbital axis are aligned within 15° to within the uncertainties of the relevant data. DS Tuc Ab is bright enough (V = 8.5) for detailed characterization using radial velocities and transmission spectroscopy.

Original languageEnglish (US)
Article numberL17
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Jul 20 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • open clusters and associations: individual (Tucana-Horologium)
  • planets and satellites: detection
  • planets and satellites: individual (HD 222259A)
  • planets and satellites: individual (TIC 410214986)
  • planets and satellites: individual (TOI 200.01)


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