Astronomers report that NASA’s Transiting Exoplanet Survey Satellite, or TESS, has detected its first Earth-sized planet lying in its parent star’s habitable zone, plus its first planet orbiting two stars.
The Earth-sized planet, known as TOI 700 d, is orbiting a cool M-dwarf star a little more than 100 light-years from Earth in the southern constellation Dorado. TESS picked up signs of three planets, but only the outermost world — TOI 700 d — orbits in the zone where it’s thought possible for water to exist at the surface in liquid form. On Earth, that’s a key requirement for habitability.
The circumbinary planet is called TOI 1338 b, and it’s in a stellar system that’s about 1,300 light-years away in the constellation Pictor. The fact that it traces an orbit around an eclipsing binary star system evokes comparisons to Tatooine, the planet with two suns that served as Luke Skywalker’s home in “Star Wars.”
This planet isn’t likely to be all that livable, however: It’s 6.9 times larger than Earth, which puts it in a class between Neptune and Saturn.
Both revelations came to light Monday in conjunction with this week’s winter meeting of the American Astronomical Society in Honolulu, a gathering that’s been called the “Super Bowl of Astronomy.” TESS was launched in 2018 and is designed to survey 200,000 of the brightest stars in our celestial neighborhood for signs of orbiting planets.
Other planet-hunting missions have detected Earth-sized, habitable-zone planets as well as circumbinary planets, but TOI 700 d and TOI 1338 b represent firsts in those categories for TESS.