TOI-700 - habitable planet candidate in multi-planet M dwarf system from TESS

TOI-700 becomes the first confirmed extrasolar planet(s) of the 2020's.

The First Habitable Zone Earth-sized Planet from TESS. I: Validation of the TOI-700 System
https://arxiv.org/abs/2001.00952

Quote :

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.

Press release:
https://www.nasa.gov/feature/goddard/2020/nasa-planet-hunter-finds-its-1st-earth-size-habitable-zone-world



The First Habitable Zone Earth-Sized Planet From TESS II: Spitzer Confirms TOI-700 d
https://arxiv.org/abs/2001.00954

The First Habitable Zone Earth-sized Planet from TESS. III: Climate States and Characterization Prospects for TOI-700 d
https://arxiv.org/abs/2001.00955

There appears to be a possibility that the space weather environment would not be overly hostile for TOI-700d:

Cohen et al. "The Space Environment and Atmospheric Joule Heating of the Habitable Zone Exoplanet TOI700-d"
https://arxiv.org/abs/2005.11587

A fourth planet in the system: an Earth-sized planet in the optimistic HZ.
https://exoplanets.nasa.gov/news/1720/second-earth-sized-world-found-in-systems-habitable-zone/