TESS, the Transiting Exoplanet Survey Satellite, was launched in 2018 with the goal of discovering small planets around the Sun’s nearest neighbors, stars bright enough to allow for follow-up characterizations of their planets’ masses and atmospheres. TESS has so far discovered seventeen small planets around eleven nearby stars that are M dwarfs — stars that are smaller than the Sun (less than about 60% of the Sun’s mass) and cooler (surface temperatures less than about 3900 kelvin). In a series of three papers that appeared together this month, astronomers report that one of these planets, TOI-700d, is Earth-sized and also located in its star’s habitable zone; they also discuss its possible climate.

CfA astronomers Joseph Rodriguez, Laura Kreidberg, Karen Collins, Samuel Quinn, Dave Latham, Ryan Cloutier, Jennifer Winters, Jason Eastman, and David Charbonneau were on the teams that studied TOI-700d, one of three small planets orbiting one M dwarf star (its mass is 0.415 solar masses) located one hundred and two light-years from Earth. The TESS data analysis found the tentative sizes of the planets as being approximately Earth-sized, 1.04, 2.65 and 1.14 Earth-radii, respectively, and their orbital periods as 9.98, 16.05, and 37.42 days, respectively.