LP 791-18 (TOI-736) is a cool M dwarf star in the constellation Crater, located 26.65lk=onNaNlk=on 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.
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.