LP 791-18

LP 791-18 (TOI-736) is a cool M dwarf star in the constellation Crater, located 26.65 pc away from Earth.

The star is one of the smallest known to host exoplanets. In 2019 two exoplanets in transit around it were announced by TESS, and a third planet was discovered in Spitzer Space Telescope data in 2023.

Planetary system
The innermost planet, b, is a super-Earth and the outermost planet, c, is a mini-Neptune. They were discovered together in 2019. The middle planet, d, is an Earth-mass world discovered in 2023. It may potentially be tidally heated by interactions with planet c, which would lead to abundant volcanoes similar to Jupiter's moon Io. As the planet d is in the inner edge of the habitable zone, liquid water could condense on the side of the planet that faces away from the host star.

In 2021 planet c was suggested for atmospheric analysis by the James Webb Space Telescope.