TOI-700: A Small Red Dwarf and Its Four Known Worlds

TOI-700 is 102 light-years away, and four planets have been cataloged around it. The host is an M2 V star, a small, cool red dwarf on the main sequence. Its reported mass estimate is 0.416 solar masses and its reported radius estimate is 0.42 solar radii, both smaller than the Sun's. Its temperature is 3480 K, cooler than the Sun's, and its age carries a reported lower limit of 1.5 billion years.

The planets were all found by the transit method, in which a world passes in front of its star from our viewpoint and produces a small dip in observed brightness. TOI-700 b, a Sub-Earth discovered in 2020, has an orbital period of 9.98 days and a radius of 0.914 Earth radii. TOI-700 c, a Neptune-like planet also announced in 2020, orbits every 16.1 days and has a radius of 2.6 Earth radii. TOI-700 d, classified as Earth-like, was announced in 2020 and completes an orbit in 37.4 days; its radius is 1.07 Earth radii. TOI-700 e is another Sub-Earth, discovered in 2023, with an orbital period of 27.8 days and a radius of 0.953 Earth radii.

Among these four, TOI-700 b has both the shortest year and the smallest radius by reported estimates, while TOI-700 c has the second-shortest year and the largest radius. TOI-700 d has the second-largest radius and the longest year, and TOI-700 e has the second-smallest radius and the second-longest year.