LP 791-18

LP 791-18

Observation data Epoch J2000      Equinox J2000
Constellation	Crater[1]
Right ascension	11^h 02^m 45.95462^s[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

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]

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]

References

1. "Finding the constellation which contains given sky coordinates". djm.cc. 2 August 2008.
2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
3. Crossfield, Ian J. M.; Waalkes, William; Newton, Elisabeth R.; Narita, Norio; Muirhead, Philip; Ment, Kristo; et al. (2019). "A Super-Earth and Sub-Neptune Transiting the Late-type M Dwarf LP 791-18". The Astrophysical Journal Letters. 883 (1): L16. arXiv:1906.09267. Bibcode:2019ApJ...883L..16C. doi:10.3847/2041-8213/ab3d30.
4. "LP 791-18". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 19 May 2023.
5. Peterson, Merrin S; Benneke, Björn; Collins, Karen; Piaulet, Caroline; Crossfield, Ian JM; Ali-Dib, Mohamad; et al. (2023). "A temperate Earth-sized planet with tidal heating transiting an M6 star". Nature. 617 (7962): 701–705. doi:10.1038/s41586-023-05934-8. hdl:11603/28165. PMID 37198481.
6. Kazmierczak, Jeanette (16 May 2023). "NASA's Spitzer, TESS Find Potentially Volcano-Covered Earth-Size World". NASA. Retrieved 19 May 2023.
7. Phillips, Caprice L.; Wang, Ji; Kendrew, Sarah; Greene, Thomas P.; Hu, Renyu; Valenti, Jeff; Panero, Wendy R.; Schulze, Joseph (2021). "Detecting Biosignatures in the Atmospheres of Gas Dwarf Planets with the James Webb Space Telescope". The Astrophysical Journal. 923 (2): 144. arXiv:2109.12132. Bibcode:2021ApJ...923..144P. doi:10.3847/1538-4357/ac29be.
8. Greklek-McKeon, Michael; Knutson, Heather A.; Levine, W. Garrett; Hu, Renyu; Saidel, Morgan; Barrientos, Jonathan Gomez; Batygin, Konstantin; Benneke, Björn (2025-01-30). "Updated Mass, Eccentricity, and Tidal Heating Constraints for the Earth-sized Planet LP 791-18". arXiv:2501.18700.