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

Abstract

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 enable 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 in the conservative habitable zone of its host star, where it receives a flux from its star that is approximately 86% of the 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 beyond. TESS is scheduled to return to the Southern Hemisphere and observe TOI-700 for an additional 11 sectors in its extended mission, which should provide further constraints on the known planet parameters and searches for additional planets and transit timing variations in the system.

exoplanet: Gradient-based probabilistic inference for exoplanet data other astronomical time series

“…While it has been used for other applications, such as the study of stellar variability (e.g., Gillen et al, 2020;Medina et al, 2020), the primary purpose of exoplanet is the characterization of exoplanets (e.g., Gilbert et al, 2020;Plavchan et al, 2020) or multiple star systems (e.g., Czekala et al, 2021) using time series photometry, astrometry, and/or radial velocity. In particular, the typical use case would be to use one or more of these datasets to place constraints on the physical and orbital parameters of the system, such as planet mass or orbital period, while simultaneously taking into account the effects of stellar variability.…”

The TESS Objects of Interest Catalog from the TESS Prime Mission

“…with a period of P = 37.42 days and an equilibrium temperature of T eq ∼ 269 K (Rodriguez et al 2020;Gilbert et al 2020;Suissa et al 2020 and lies in the southern TESS continuous viewing zone. The system was one of the last targets Spitzer observed.…”

Circumbinary Habitable Zones in the Presence of a Giant Planet

“…Improvements in detection techniques have now reached a point where finding planets of similar size to our Earth has become a reality. Four of the planets in the Trappist-1 system (Gillon et al, 2016) or TOI-700d (Gilbert et al, 2020;Rodriguez et al, 2020) are prime examples. Several planets in those systems orbit their host star inside the habitable zone.…”