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The First Habitable Zone Earth-sized Planet from TESS. I: Validation of the TOI-700 System

Gilbert, Emily A. and Barclay, Thomas and Schlieder, Joshua E. and Quintana, Elisa V. and Hord, Benjamin J. and Kostov, Veselin B. and Lopez, Eric D. and Rowe, Jason F. and Hoffman, Kelsey and Walkowicz, Lucianne M. and Silverstein, Michele L. and Rodriguez, Joseph E. and Vanderburg, Andrew and Suissa, Gabrielle and Airapetian, Vladimir S. and Clement, Matthew S. and Raymond, Sean N. and Mann, Andrew W. and Kruse, Ethan and Lissauer, Jack J. and Colón, Knicole D. and Kopparapu, Ravi kumar and Kreidberg, Laura and Zieba, Sebastian and Collins, Karen A. and Quinn, Samuel N. and Howell, Steve B. and Ziegler, Carl and Vrijmoet, Eliot Halley and Adams, Fred C. and Arney, Giada N. and Boyd, Patricia T. and Brande, Jonathan and Burke, Christopher J. and Cacciapuoti, Luca and Chance, Quadry and Christiansen, Jessie L. and Covone, Giovanni and Daylan, Tansu and Dineen, Danielle and Dressing, Courtney D. and Essack, Zahra and Fauchez, Thomas J. and Galgano, Brianna and Howe, Alex R. and Kaltenegger, Lisa and Kane, Stephen R. and Lam, Christopher and Lee, Eve J. and Lewis, Nikole K. and Logsdon, Sarah E. and Mandell, Avi M. and Monsue, Teresa and Mullally, Fergal and Mullally, Susan E. and Paudel, Rishi and Pidhorodetska, Daria and Plavchan, Peter and Tañón Reyes, Naylynn and Rinehart, Stephen A. and Rojas-Ayala, Bárbara and Smith, Jeffrey C. and Stassun, Keivan G. and Tenenbaum, Peter and Vega, Laura D. and Villanueva, Geronimo L. and Wolf, Eric T. and Youngblood, Allison and Ricker, George R. and Vanderspek, Roland K. and Latham, David W. and Seager, Sara and Winn, Joshua N. and Jenkins, Jon M. and Bakos, Gáspár Á. and Briceño, César and Ciardi, David R. and Cloutier, Ryan and Conti, Dennis M. and Couperus, Andrew and Di Sora, Mario and Eisner, Nora L. and Everett, Mark E. and Gan, Tianjun and Hartman, Joel D. and Henry, Todd and Isopi, Giovanni and Jao, Wei-Chun and Jensen, Eric L. N. and Law, Nicholas and Mallia, Franco and Matson, Rachel A. and Shappee, Benjamin J. and Wood, Mackenna Lee and Winters, Jennifer G. (2020) The First Habitable Zone Earth-sized Planet from TESS. I: Validation of the TOI-700 System. Astronomical Journal, 160 (3). Art. No. 116. ISSN 1538-3881. doi:10.3847/1538-3881/aba4b2.

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We 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Barclay, Thomas0000-0001-7139-2724
Schlieder, Joshua E.0000-0001-5347-7062
Quintana, Elisa V.0000-0003-1309-2904
Hord, Benjamin J.0000-0001-5084-4269
Kostov, Veselin B.0000-0001-9786-1031
Rowe, Jason F.0000-0002-5904-1865
Walkowicz, Lucianne M.0000-0003-2918-8687
Silverstein, Michele L.0000-0003-2565-7909
Rodriguez, Joseph E.0000-0001-8812-0565
Vanderburg, Andrew0000-0001-7246-5438
Suissa, Gabrielle0000-0003-4471-1042
Airapetian, Vladimir S.0000-0003-4452-0588
Clement, Matthew S.0000-0001-8933-6878
Raymond, Sean N.0000-0001-8974-0758
Mann, Andrew W.0000-0003-3654-1602
Kruse, Ethan0000-0002-0493-1342
Lissauer, Jack J.0000-0001-6513-1659
Colón, Knicole D.0000-0001-8020-7121
Kopparapu, Ravi kumar0000-0002-5893-2471
Kreidberg, Laura0000-0003-0514-1147
Zieba, Sebastian0000-0003-0562-6750
Collins, Karen A.0000-0001-6588-9574
Quinn, Samuel N.0000-0002-8964-8377
Howell, Steve B.0000-0002-2532-2853
Ziegler, Carl0000-0002-0619-7639
Vrijmoet, Eliot Halley0000-0002-1864-6120
Boyd, Patricia T.0000-0003-0442-4284
Burke, Christopher J.0000-0002-7754-9486
Christiansen, Jessie L.0000-0002-8035-4778
Covone, Giovanni0000-0002-2553-096X
Daylan, Tansu0000-0002-6939-9211
Dressing, Courtney D.0000-0001-8189-0233
Essack, Zahra0000-0002-2482-0180
Fauchez, Thomas J.0000-0002-5967-9631
Galgano, Brianna0000-0001-5379-4295
Howe, Alex R.0000-0002-4884-7150
Kaltenegger, Lisa0000-0002-0436-1802
Kane, Stephen R.0000-0002-7084-0529
Lee, Eve J.0000-0002-1228-9820
Lewis, Nikole K.0000-0002-8507-1304
Logsdon, Sarah E.0000-0002-9632-9382
Mandell, Avi M.0000-0002-8119-3355
Monsue, Teresa0000-0003-3896-3059
Mullally, Susan E.0000-0001-7106-4683
Paudel, Rishi0000-0002-8090-3570
Pidhorodetska, Daria0000-0001-9771-7953
Plavchan, Peter0000-0002-8864-1667
Rojas-Ayala, Bárbara0000-0002-0149-1302
Smith, Jeffrey C.0000-0002-6148-7903
Stassun, Keivan G.0000-0002-3481-9052
Tenenbaum, Peter0000-0002-1949-4720
Villanueva, Geronimo L.0000-0002-2662-5776
Wolf, Eric T.0000-0002-7188-1648
Youngblood, Allison0000-0002-1176-3391
Ricker, George R.0000-0003-2058-6662
Vanderspek, Roland K.0000-0001-6763-6562
Latham, David W.0000-0001-9911-7388
Seager, Sara0000-0002-6892-6948
Winn, Joshua N.0000-0002-4265-047X
Jenkins, Jon M.0000-0002-4715-9460
Bakos, Gáspár Á.0000-0001-7204-6727
Briceño, César0000-0001-7124-4094
Ciardi, David R.0000-0002-5741-3047
Cloutier, Ryan0000-0001-5383-9393
Conti, Dennis M.0000-0003-2239-0567
Everett, Mark E.0000-0002-0885-7215
Gan, Tianjun0000-0002-4503-9705
Hartman, Joel D.0000-0001-8732-6166
Henry, Todd0000-0002-9061-2865
Isopi, Giovanni0000-0002-8458-0588
Jao, Wei-Chun0000-0003-0193-2187
Jensen, Eric L. N.0000-0002-4625-7333
Law, Nicholas0000-0001-9380-6457
Matson, Rachel A.0000-0001-7233-7508
Shappee, Benjamin J.0000-0003-4631-1149
Wood, Mackenna Lee0000-0001-7336-7725
Winters, Jennifer G.0000-0001-6031-9513
Additional Information:© 2020 The American Astronomical Society. Received 2019 December 24; revised 2020 July 2; accepted 2020 July 10; published 2020 August 14. This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by NASA's Science Mission directorate. We acknowledge the use of public TESS Alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC; Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Some of the observations in the paper made use of the High-Resolution Imaging instrument Zorro at Gemini South. Zorro was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This work makes use of observations from the LCOGT network. E.A.G. thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining grant #1829740, the Brinson Foundation, and the Moore Foundation; her participation in the program has benefited this work. E.A.G. and E.V.Q. are thankful for support from GSFC Sellers Exoplanet Environments Collaboration (SEEC), which is funded by the NASA Planetary Science Division's Internal Scientist Funding Model. J.F.R. acknowledges research funding support from the Canada Research Chairs program and NSERC Discovery Program. This research was enabled, in part, by support provided by Calcul Québec ( and ComputeCanada ( A.V.'s work was performed under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. R.C. is supported by a NASA grant in support of the TESS science mission. C.D.D acknowledges support from the NASA TESS Guest Investigator Program through grant 80NSSC18K1583. B.J.S. is supported by NASA grant 80NSSC19K1717 and NSF grants AST-1908952, AST-1920392, and AST-1911074. B.R-A acknowledges the funding support from FONDECYT through grant 11181295. J.G.W. is supported by a grant from the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. T.D. acknowledges support from MIT's Kavli Institute as a Kavli postdoctoral fellow. V.S.A. was supported by Sellers Exoplanetary Environments Collaboration (SEEC) Internal Scientist Funding Model (ISFM) at NASA GSFC and NICER Cycle 1 GO program. Facilities: ASAS-SN - , CTIO:0.9 m (2048x2046 Tek2K CCD) - , CTIO:1.5 m (CHIRON) - , Exoplanet Archive - , Gaia - , Gemini:South (Zorro) - , MAST - , LCOGT - , SOAR (Goodman Spectrograph - , HRcam) - , TESS - , WISE - Software: AstroImageJ (Collins et al. 2017), astropy (Astropy Collaboration et al. 2013, 2018), celerite (Foreman-Mackey et al. 2017; Foreman-Mackey 2018), emcee (Foreman-Mackey et al. 2013), exoplanet (Foreman-Mackey 2018), DAVE (Kostov et al. 2019a), Forecaster (Chen & Kipping 2017), IPython (Perez & Granger 2007), Jupyter (Kluyver et al. 2016), Lightkurve (Lightkurve Collaboration et al. 2018), M_-M_K- (Mann et al. 2019), Matplotlib (Hunter 2007), Mercury6 (Chambers 1999), NumPy (van der Walt et al. 2011), Pandas (McKinney 2010), PyMC3 (Salvatier et al. 2016), SciPy (Oliphant 2007), stardate (Angus et al. 2019a, 2019b), STARRY (Luger et al. 2018; Agol et al. 2020), Tapir (Jensen 2013), TRANSITFIT5 (Rowe et al. 2015; Rowe 2016), Theano (Theano Development Team 2016), TTVFast (Deck et al. 2014), TTV2Fast2Furious (Hadden et al. 2019), vespa (Morton 2012, 2015)
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Gaia Multilateral AgreementUNSPECIFIED
LSSTC Institutional MembersUNSPECIFIED
Brinson FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Canada Research Chairs ProgramUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)11181295
John Templeton FoundationUNSPECIFIED
Massachusetts Institute of Technology (MIT)UNSPECIFIED
Subject Keywords:Exoplanet systems; Transit photometry; Low mass stars; M dwarf stars; Astronomy data analysis
Issue or Number:3
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet systems (484); Transit photometry (1709); Low mass stars (2050); M dwarf stars (982); Astronomy data analysis (1858)
Record Number:CaltechAUTHORS:20200611-113656604
Persistent URL:
Official Citation:Emily A. Gilbert et al 2020 AJ 160 116
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103844
Deposited By: George Porter
Deposited On:12 Jun 2020 14:44
Last Modified:16 Nov 2021 18:25

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