LHS 1140

Artist's impression of LHS 1140 and LHS 1140b.
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cetus
Right ascension	00h 44m 59.33091s[1]
Declination	−15° 16′ 17.5428″[1]
Apparent magnitude (V)	14.18[2]
Characteristics
Evolutionary stage	Red dwarf
Spectral type	M4.5V[2]
Astrometry
Radial velocity (Rv)	−13.74±0.42[1] km/s
Proper motion (μ)	RA: 318.152mas/yr[1] Dec.: −596.623mas/yr[1]
Parallax (π)	66.8287±0.0479 mas[1]
Distance	48.80 ± 0.03 ly (14.96 ± 0.01 pc)
Details[3]
Mass	0.1844±0.0045 M☉
Radius	0.2159±0.0030 R☉
Luminosity	0.0038±0.0003 L☉
Surface gravity (log g)	5.041±0.016 cgs
Temperature	3,096±48 K
Metallicity[Fe/H]	−0.15±0.09 dex
Rotation	131±5 d
Age	>5 Gyr
Other designations
GJ 3053,G 270-58,G 268-38,LHS 1140,NLTT 2465,TOI-256,TIC 92226327,2MASS J00445930-1516166[4]
Database references
SIMBAD	data
Exoplanet Archive	data
ARICNS	data

LHS 1140 is ared dwarf star in theconstellation ofCetus. Based onstellar parallax measurement, it is 48.8light-years (15.0parsecs) away from theSun.^[1] 'LHS' refers to theLuyten Half-Second Catalogue of stars withproper motions exceedinghalf a second of arc annually.^[5] The star is over 5 billion years old and has only about 18% the mass of the Sun and 21% of its radius.^[6]LHS 1140's rotational period is 130 days. No flares have been observed.^[7]

As of October 2023, LHS 1140 is known to have two planets orbiting it. The inner planet is LHS 1140 c, a hot rocky planet; the outer planet, which was the first to be discovered, is LHS 1140 b, a water-rich super-Earth in the habitable zone.^[3]

The existence of LHS 1140 c was first proposed by Feng et al. in July 2018^[8] and confirmed by Ment et al. in August 2018, using thetransit method of detection. It has a mass about 1.9 times Earth's and a radius 1.3 times as large, giving it a density of about5 g/cm³,^[9] consistent with a rocky composition.^[3] From eclipse observations, its dayside temperature has been measured at561±44 K, consistent with a low-albedo planet with no atmosphere. The observations rule out pureCO₂ atmospheres with a pressure≥10 mbar and pureH₂O atmospheres≥1 bar. This result is similar to other hot rocky planets around red dwarfs, such asLHS 3844 b andTRAPPIST-1b.^[10]

LHS 1140 b was discovered by theMEarth Project in 2017 using the transit method.^[2] Follow-up radial velocities were measured by theHigh Accuracy Radial Velocity Planet Searcher instrument to confirm the planet and measure its mass.^[7] The planet LHS 1140 b is asuper-Earth in thehabitable zone and transits the star every 24.7 days. This allows its atmosphere to be studied: the combination of the transiting super-Earth and the relatively small and nearby host star make this system one of the most promising known for atmosphere studies, along with theTRAPPIST-1 system.^[2][11] Observations by theHubble Space Telescope in 2020 found signs ofwater vapor in the planet's atmosphere, but this has not been confirmed.^[12] Later observations with theJames Webb Space Telescope (JWST) suggest the presence of anitrogen-rich atmosphere.^[13][14]

LHS 1140 b was initially estimated to be about 7 times Earth's mass and about 1.4 times its radius, suggesting a dense rocky planet.^[2] Later studies in 2018 and 2020 revised the radius upwards to about 1.7 times Earth's, giving it a density of about7.5 g/cm³, still consistent with a rocky composition.^[9][15] However, a 2023 study measuring the planet's mass and radius with greater precision found a lower mass of about 5.6 times Earth's, and a correspondingly lower density, no longer consistent with a rocky planet given the planet's size. LHS 1140 b is likely anocean world with 9-19% of its mass composed of water;^[3] JWST observations rule out a hydrogen atmosphere, so it is not amini-Neptune.^[13][14]

In July 2018, Feng et al. published a reanalysis of theradial velocity data for LHS 1140, and proposed the likely existence of two additional planets: an inner Earth-mass planet orbiting every 3.8 days (later confirmed as planet c) and an outer Neptune-mass planet orbiting every 90 days.^[8] The orbital period of the outer planet candidate, LHS 1140 d, was refined to 78 days in 2020,^[15] but this radial velocity signal was found to originate from stellar activity rather than a planet in 2023.^[3]

• Cetus
• M-type main-sequence stars
• Planetary systems with two confirmed planets
• Gliese and GJ objects
• TESS Objects of Interest

• Articles with short description
• Short description matches Wikidata
• Use dmy dates from June 2022