Planets of LP 791-18

LP 791-18 is a small, cool red dwarf star 86.4 light-years away. Its spectral type, M(6.1+/-0.7) V, confirms it as an M-type main-sequence star. The host is accompanied by three known planets. Its reported mass estimate is 0.139 solar masses and its reported radius estimate is 0.171 solar radii, both smaller than the Sun's. The star's reported temperature is 2960 K, cooler than the Sun's, and it has a reported lower limit of 0.5 billion years for its age.

All three planets were found by the transit method, in which a planet passing in front of its star from our viewpoint causes a small dip in observed brightness. Repeated dips help establish orbital periods.

LP 791-18 b, discovered in 2019, is an Earth-like planet with an orbital period of 0.948 days and a radius of 1.21 Earth radii. Among the listed planets, it has the shortest year and the second-smallest radius.

LP 791-18 c, also discovered in 2019, is a Super-Earth with an orbital period of 4.99 days. It has a mass of 7.16 Earth masses and a radius of 2.49 Earth radii. Its mean density is 2.56 g/cm³, 0.465 times Earth's. Among the listed planets, it has the longest year and the largest radius. Its reported radius estimate is larger than Earth's, and its reported mass estimate is also larger than Earth's.

LP 791-18 d, discovered in 2023, is an Earth-like planet with an orbital period of 2.75 days. It has a mass of 0.91 Earth masses and a radius of 1.03 Earth radii. Its mean density is 4.56 g/cm³, 0.828 times Earth's. Among the listed planets, it has the second-shortest year and the smallest radius.