Barclay, ThomasPaudel, Rishi R.et al.Pidhorodetska, Daria2021-01-252021-01-252020-08-14Barclay, Thomas; Paudel, Rishi R.; et al.; The First Habitable-zone Earth-sized Planet from TESS. I. Validation of the TOI-700 System; The Astronomical Journal, Volume 160, Number 3 (2020); https://iopscience.iop.org/article/10.3847/1538-3881/aba4b2https://doi.org/10.3847/1538-3881/aba4b2http://hdl.handle.net/11603/20608Emily A. Gilbert1,2,3,4, Thomas Barclay3,5, Joshua E. Schlieder3, Elisa V. Quintana3, Benjamin J. Hord3,6, Veselin B. Kostov3, Eric D. Lopez3, Jason F. Rowe7, Kelsey Hoffman8, Lucianne M. Walkowicz2, Michele L. Silverstein3,9,55, Joseph E. Rodriguez10, Andrew Vanderburg11,56, Gabrielle Suissa3,4,12, Vladimir S. Airapetian3,4, Matthew S. Clement13, Sean N. Raymond14, Andrew W. Mann15, Ethan Kruse3, Jack J. Lissauer16, Knicole D. Colón3, Ravi kumar Kopparapu3,4, Laura Kreidberg10, Sebastian Zieba17, Karen A. Collins10, Samuel N. Quinn10, Steve B. Howell16, Carl Ziegler18, Eliot Halley Vrijmoet9,19, Fred C. Adams20, Giada N. Arney3,4, Patricia T. Boyd3, Jonathan Brande3,4,6, Christopher J. Burke21, Luca Cacciapuoti22, Quadry Chance23, Jessie L. Christiansen24, Giovanni Covone22,25,26, Tansu Daylan27,57, Danielle Dineen7, Courtney D. Dressing28, Zahra Essack29,30, Thomas J. Fauchez4,12, Brianna Galgano31, Alex R. Howe3, Lisa Kaltenegger32, Stephen R. Kane33, Christopher Lam3, Eve J. Lee34, Nikole K. Lewis32, Sarah E. Logsdon35, Avi M. Mandell3,4, Teresa Monsue3, Fergal Mullally8, Susan E. Mullally36, Rishi R. Paudel4,5, Daria Pidhorodetska3, Peter Plavchan37, Naylynn Tañón Reyes3,38, Stephen A. Rinehart3, Bárbara Rojas-Ayala39, Jeffrey C. Smith8,16, Keivan G. Stassun40,41, Peter Tenenbaum8,16, Laura D. Vega3,40, Geronimo L. Villanueva3,4, Eric T. Wolf4,42, Allison Youngblood43, George R. Ricker27, Roland K. Vanderspek27, David W. Latham10, Sara Seager29,27,44, Joshua N. Winn45, Jon M. Jenkins16, Gáspár Å. Bakos46,58,59, César Briceño47, David R. Ciardi48, Ryan Cloutier10, Dennis M. Conti49, Andrew Couperus9,19, Mario Di Sora50, Nora L. Eisner51, Mark E. Everett35, Tianjun Gan52, Joel D. Hartman46, Todd Henry9, Giovanni Isopi50, Wei-Chun Jao19, Eric L. N. Jensen53, Nicholas Law15, Franco Mallia50, Rachel A. Matson16, Benjamin J. Shappee54, Mackennae Le Wood15, and Jennifer G. WintersWe present the discovery and validation of a three-planet system orbiting the nearby (31.1 pc) M2 dwarf star TOI-700 (TIC 150428135). TOI-700 lies in the TESS continuous viewing zone in the Southern Ecliptic Hemisphere; observations spanning 11 sectors reveal three planets with radii ranging from 1 R ⊕ to 2.6 R ⊕ and orbital periods ranging from 9.98 to 37.43 days. Ground-based follow-up combined with diagnostic vetting and validation tests enables us to rule out common astrophysical false-positive scenarios and validate the system of planets. The outermost planet, TOI-700 d, has a radius of 1.19 ± 0.11 R ⊕ and resides within a conservative estimate of the host star's habitable zone, where it receives a flux from its star that is approximately 86% of Earth's insolation. In contrast to some other low-mass stars that host Earth-sized planets in their habitable zones, TOI-700 exhibits low levels of stellar activity, presenting a valuable opportunity to study potentially rocky planets over a wide range of conditions affecting atmospheric escape. While atmospheric characterization of TOI-700 d with the James Webb Space Telescope (JWST) will be challenging, the larger sub-Neptune, TOI-700 c (R = 2.63 R ⊕), will be an excellent target for JWST and future space-based observatories. TESS is scheduled to once again observe the Southern Hemisphere, and it will monitor TOI-700 for an additional 11 sectors in its extended mission. These observations should allow further constraints on the known planet parameters and searches for additional planets and transit timing variations in the system.21 pagesen-USThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.Public Domain Mark 1.0This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.Text