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LHS 1140

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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: 318.152 mas/yr[1]
Dec.: −596.623 mas/yr[1]
Parallax (π)66.8287 ± 0.0479 mas[1]
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, TOI-256, TIC 92226327, 2MASS J00445930-1516166[4]
Database references
SIMBADdata
ARICNSdata

LHS 1140 is a red dwarf 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 confirmed planets orbiting it.[3]

The first to be discovered was LHS 1140 b, 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 the mass.[7] The planet LHS 1140 b is a super-Earth in the habitable zone and transits the star every 24.7 days. This should allow its atmosphere to be studied in future: 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][8] Observations by the Hubble Space Telescope in 2020 found signs of water vapor in the planet's atmosphere, but this has not been confirmed.[9]

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.[10][11] 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) or a dense mini-Neptune.[3]

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 and an outer Neptune-mass planet orbiting every 90 days.[12] In August 2018, Ment et al., using the transit method of detection, confirmed the existence of the inner planet LHS 1140 c with a mass about 1.8 times Earth's and a radius 1.3 times as large, giving it a density of about 5 g/cm3,[10] consistent with a rocky composition.[3]

The orbital period of the outer planet candidate LHS 1140 d was refined to 78 days in 2020,[11] 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. ^ a b c d e f 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.
  2. ^ a b c d e 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. arXiv:1704.05556. Bibcode:2017Natur.544..333D. doi:10.1038/nature22055. PMID 28426003. S2CID 2718408.
  3. ^ a b c d e f 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. arXiv:2310.15490. Bibcode:2024ApJ...960L...3C. doi:10.3847/2041-8213/ad1691. ISSN 2041-8205.
  4. ^ "G 268-38". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 16 October 2020.
  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. arXiv:2106.07656. Bibcode:2021ApJ...918...40P. doi:10.3847/1538-4357/ac0aea. S2CID 235435757. 40.
  7. ^ a b Dickinson, David (19 April 2017). "Welcome to LHS 1140b: A super-Earth in the habitable zone". Sky & Telescope. Retrieved 19 April 2017.
  8. ^ Overbye, Dennis (19 April 2017). "A new exoplanet may be most promising yet in search for life". The New York Times. Retrieved 20 April 2017.
  9. ^ Edwards, Billy; Changeat, Quentin; Mori, Mayuko; Anisman, Lara O.; Morvan, Mario; Kai Hou Yip; Tsiaras, Angelos; Al-Refaie, Ahmed; Waldmann, Ingo; Tinetti, Giovanna (2020). "Hubble WFC3 Spectroscopy of the Habitable-zone Super-Earth LHS 1140 b". The Astronomical Journal. 161 (1): 44. arXiv:2011.08815. Bibcode:2021AJ....161...44E. doi:10.3847/1538-3881/abc6a5. S2CID 226975730.
  10. ^ a b Kristo Ment; Jason A. Dittmann; Nicola Astudillo-Defru; David Charbonneau; Jonathan Irwin; Xavier Bonfils; Felipe Murgas; Jose-Manuel Almenara; Thierry Forveille; Eric Agol; Sarah Ballard; Zachory K. Berta-Thompson; Franc¸ois Bouchy; Ryan Cloutier; Xavier Delfosse; Rene Doyon; Courtney D. Dressing; Gilbert A. Esquerdo; Raphaelle D. Haywood; David M. Kipping; David W. Latham; Christophe Lovis; Elisabeth R. Newton; Francesco Pepe; Joseph E. Rodriguez; Nuno C. Santos; Thiam-Guan Tan; Stephane Udry; Jennifer G. Winters; Anael Wunsche (3 August 2018). "A Second Terrestrial Planet Orbiting the Nearby M Dwarf LHS 1140". The Astronomical Journal. 157 (1): 32. arXiv:1808.00485. Bibcode:2019AJ....157...32M. doi:10.3847/1538-3881/aaf1b1. S2CID 119504366.
  11. ^ a b 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. arXiv:2010.06928. Bibcode:2020A&A...642A.121L. doi:10.1051/0004-6361/202038922.
  12. ^ 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].
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