LP 791-18

LP 791-18 (TOI-736) is a cool M dwarf star in the constellation Crater, located 26.65 parsecs (86.9 light-years) away from Earth.^[3]

LP 791-18

Observation data Epoch J2000      Equinox J2000
Constellation	Crater[1]
Right ascension	11h 02m 45.95462s[2]
Declination	−16° 24′ 22.2882″[2]
Apparent magnitude (V)	16.9±0.2[3]
Characteristics
Evolutionary stage	Red dwarf (main sequence)
Spectral type	M6.1±0.7V[3]
Astrometry
Proper motion (μ)	RA: -221.291 mas/yr[2] Dec.: -58.841 mas/yr[2]
Parallax (π)	37.5225±0.0392 mas[2]
Distance	86.92 ± 0.09 ly (26.65 ± 0.03 pc)
Details[3]
Mass	0.139±0.005 M☉
Radius	0.17±0.018 R☉
Temperature	2960±55 K
Metallicity [Fe/H]	-0.09±0.19 dex
Age	0.5±0.064 Gyr
Other designations
LP 791-18, TOI-736, TIC 181804752, 2MASS J11024596-1624222[4]
Database references
SIMBAD	data

The star is one of the smallest known to host exoplanets.^[5] In 2019 two exoplanets in transit around it were announced by TESS,^[3] and a third planet was discovered in Spitzer Space Telescope data in 2023.^[5]

Planetary system

Artist's impression of LP 791-18 d, with c in the background^[6]

The innermost planet, b, is a super-Earth and the outermost planet, c, is a mini-Neptune. They were discovered together in 2019.^[3] 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.^[5] 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.^[6]

In 2021 planet c was suggested for atmospheric analysis by the James Webb Space Telescope.^[7]

The LP 791-18 planetary system^[a]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	—	0.00978±0.00012	0.9479981±0.0000021	—	88.37+0.94 −0.95°	1.212+0.059 −0.058 R🜨
d	0.91±0.19 M🜨	0.01992±0.00014	2.753436±0.000013	0.0011+0.0010 −0.0008	89.34±0.41°	1.032+0.044 −0.043 R🜨
c	7.16±0.65 M🜨	0.02961+0.00035 −0.00036	4.9899100+0.0000012 −0.0000014	0.0001±0.0001	89.94±0.05°	2.488±0.096 R🜨

Notes

1. Planet b: Peterson et al. (2021)^[5]
   Semi-major axes: Peterson et al. (2021)^[5]
   Planet c: Greklek-McKeon et al. (2025)^[8]
   Planet d's mass and eccentricity: Greklek-McKeon et al. (2025);^[8] miscellaneous properties from Peterson et al. (2021).^[5]