NASA's planet-hunting mission TESS has found its first potentially habitable exoplanet the size of Earth orbiting a star about 100 light-years from Earth, according to the agency. The planet is part of a multi-planet system around TOI 700, a small, cool M-dwarf star in the Dorado constellation. It's only about 40% of our sun's mass and size, with half of the surface temperature. The planet is known as TOI 700 d, one of three orbiting the star. It's at just the right distance to support liquid water on the surface in the star's habitable zone. (Photo/NASA)
