Astronomy:LHS 1140

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Short description: Star in the constellation Cetus
LHS 1140
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Artist's impression of LHS 1140 and LHS 1140b.
Observation data
Equinox J2000.0]] (ICRS)
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: 318.152[1] mas/yr
Dec.: −596.623[1] mas/yr
Parallax (π)66.8287 ± 0.0479[1] mas
Distance48.80 ± 0.03 ly
(14.96 ± 0.01 pc)
Details[3]
Mass0.1844±0.0045 M☉
Radius0.2159±0.0030 R☉
Luminosity0.0038±0.0003 L☉
Surface gravity (log g)5.041±0.016 cgs
Temperature3,096±48 K
Metallicity [Fe/H]−0.15±0.09 dex
Rotation131±5 d
Age>5 Gyr
Other designations
GJ 3053, G 270-58, G 268-38, LHS 1140, NLTT 2465, 2MASS J00445930-1516166[4]
Database references
SIMBADdata
Exoplanet Archivedata
ARICNSdata

LHS 1140 is a red dwarf star in the constellation of Cetus. Based on stellar parallax measurement, it is 48.8 light-years (15.0 parsecs) away from the Sun.[1] 'LHS' refers to the Luyten Half-Second Catalogue of stars with proper motions exceeding half 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]

Planetary system

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]

LHS 1140 c

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 the transit 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 about 5 g/cm3,[9] consistent with a rocky composition.[3] From eclipse observations, its dayside temperature has been measured at 561±44 K, consistent with a low-albedo planet with no atmosphere. The observations rule out pure CO2 atmospheres with a pressure ≥10 mbar and pure H2O atmospheres ≥1 bar. This result is similar to other hot rocky planets around red dwarfs, such as LHS 3844 b and TRAPPIST-1b.[10]

LHS 1140 b

Main article: Astronomy:LHS 1140 b

LHS 1140 b was discovered by the MEarth Project in 2017 using the transit method.[2] Follow-up radial velocities were measured by the High Accuracy Radial Velocity Planet Searcher instrument to confirm the planet and measure its mass.[7] The planet LHS 1140 b is a super-Earth in the habitable 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 the TRAPPIST-1 system.[2][11] Observations by the Hubble Space Telescope in 2020 found signs of water vapor in the planet's atmosphere, but this has not been confirmed.[12] Later observations with the James Webb Space Telescope (JWST) suggest the presence of a nitrogen-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 about 7.5 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 an ocean world with 9-19% of its mass composed of water;[3] JWST observations rule out a hydrogen atmosphere, so it is not a mini-Neptune.[13][14]

Search for additional planets

In July 2018, Feng et al. published a reanalysis of the radial 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]

Size comparison of the two known planets of LHS 1140 (artistic concept) with Earth
The LHS 1140 planetary system[3]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
c 1.91±0.06 M⊕ 0.0270±0.0005 3.777940±0.000002 <0.050 89.80+0.14
−0.19° 		1.272±0.026 R⊕
b 5.60±0.19 M⊕ 0.0946±0.0017 24.73723±0.00002 <0.043 89.86±0.04° 1.730±0.025 R⊕

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Dittmann, Jason A.; Irwin, Jonathan M.; Charbonneau, David; Bonfils, Xavier; Astudillo-Defru, Nicola; Haywood, Raphaëlle D. et al. (2017). "A temperate rocky super-Earth transiting a nearby cool star". Nature 544 (7650): 333–336. doi:10.1038/nature22055. PMID 28426003. Bibcode: 2017Natur.544..333D. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Cadieux, Charles; Plotnykov, Mykhaylo; Doyon, René et al. (3 January 2024). "New Mass and Radius Constraints on the LHS 1140 Planets: LHS 1140 b Is either a Temperate Mini-Neptune or a Water World". The Astrophysical Journal Letters 960 (1): L3. doi:10.3847/2041-8213/ad1691. ISSN 2041-8205. Bibcode: 2024ApJ...960L...3C. 
  4. ↑ "G 268-38". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=G+268-38. 
  5. ↑ Luyten, Willem Jacob (1979). Catalogue of stars with proper motions exceeding 0.5" annually. University of Minnesota Press. 
  6. ↑ Pineda, J. Sebastian; Youngblood, Allison; France, Kevin (September 2021). "The M-dwarf Ultraviolet Spectroscopic Sample. I. Determining Stellar Parameters for Field Stars". The Astrophysical Journal 918 (1): 23. doi:10.3847/1538-4357/ac0aea. 40. Bibcode: 2021ApJ...918...40P. 
  7. ↑ 7.0 7.1 Dickinson, David (19 April 2017). "Welcome to LHS 1140b: A super-Earth in the habitable zone". http://www.skyandtelescope.com/astronomy-news/welcome-lhs-1140b-super-earth-habitable-zone/. 
  8. ↑ 8.0 8.1 Feng, Fabo; Tuomi, Mikko; Jones, Hugh R. A. (2018). "Minimizing the bias in exoplanet detection – application to radial velocities of LHS 1140". arXiv:1807.02483 [astro-ph.EP].
  9. ↑ 9.0 9.1 Kristo Ment; Jason A. Dittmann; Nicola Astudillo-Defru; David Charbonneau; Jonathan Irwin; Xavier Bonfils; Felipe Murgas; Jose-Manuel Almenara et al. (3 August 2018). "A Second Terrestrial Planet Orbiting the Nearby M Dwarf LHS 1140". The Astronomical Journal 157 (1): 32. doi:10.3847/1538-3881/aaf1b1. Bibcode: 2019AJ....157...32M. 
  10. ↑ Fortune, Mark et al. (May 2025). "Hot Rocks Survey III: A deep eclipse for LHS 1140c and a new Gaussian process method to account for correlated noise in individual pixels". Astronomy & Astrophysics. doi:10.1051/0004-6361/202554198. 
  11. ↑ Overbye, Dennis (19 April 2017). "A new exoplanet may be most promising yet in search for life". The New York Times. https://www.nytimes.com/2017/04/19/science/exoplanet-signs-of-life.html. 
  12. ↑ Edwards, Billy; Changeat, Quentin; Mori, Mayuko; Anisman, Lara O.; Morvan, Mario; Kai Hou Yip; Tsiaras, Angelos; Al-Refaie, Ahmed et al. (2020). "Hubble WFC3 Spectroscopy of the Habitable-zone Super-Earth LHS 1140 b". The Astronomical Journal 161 (1): 44. doi:10.3847/1538-3881/abc6a5. Bibcode: 2021AJ....161...44E. 
  13. ↑ 13.0 13.1 Damiano, Mario et al. (June 2024). "LHS 1140 b Is a Potentially Habitable Water World". The Astrophysical Journal Letters 968 (2): L22. doi:10.3847/2041-8213/ad5204. Bibcode: 2024ApJ...968L..22D. 
  14. ↑ 14.0 14.1 Cadieux, Charles et al. (July 2024). "Transmission Spectroscopy of the Habitable Zone Exoplanet LHS 1140 b with JWST/NIRISS". The Astrophysical Journal Letters 970 (1): L2. doi:10.3847/2041-8213/ad5afa. Bibcode: 2024ApJ...970L...2C. 
  15. ↑ 15.0 15.1 Lillo-Box, J.; Figueira, P.; Leleu, A.; Acuña, L.; Faria, J. P.; Hara, N. et al. (2020). "Planetary system LHS 1140 revisited with ESPRESSO and TESS". Astronomy & Astrophysics 642: A121. doi:10.1051/0004-6361/202038922. Bibcode: 2020A&A...642A.121L. 



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