LHS 475

LHS 475
	; Artist's impression of LHS 475 b and its host star
Observation data; Epoch J2000 Equinox J2000
Constellation	Octans
Right ascension	19h 20m 54.37612s
Declination	−82° 33′ 16.1679″
Apparent magnitude (V)	12.69
Characteristics
Evolutionary stage	Main sequence
Spectral type	M3.5V
Apparent magnitude (V)	12.69±0.03
Apparent magnitude (G)	11.413±0.003
Apparent magnitude (J)	8.555±0.030
Apparent magnitude (H)	8.004±0.038
Apparent magnitude (K)	7.686±0.042
Astrometry
Radial velocity (Rv)	−10.59±0.24 km/s
Proper motion (μ)	RA: +342.300 mas/yr ; Dec.: −1230.297 mas/yr
Parallax (π)	80.1134 ± 0.0206 mas
Distance	40.71 ± 0.01 ly ; (12.482 ± 0.003 pc)
Details
Mass	0.274±0.015 M☉
Radius	0.2789±0.0014 R☉
Luminosity (bolometric)	0.00862±0.00039 L☉
Surface gravity (log g)	4.964±0.046 cgs
Temperature	3289±83 K
Rotation	79.317 d
Other designations
	GJ 4102, L 22-69, LFT 1458, LHS 475, LTT 7606, NLTT 47504, PM J19209-8233, TOI-910, TIC 369327947, 2MASS J19205439-8233170
Database references
SIMBAD	data

LHS 475 is a red dwarf star located 40.7 light-years (12.5 parsecs) away from the Solar System in the constellation of Octans. It hosts one known exoplanet.^[6]^[7]

Planetary system

The exoplanet LHS 475 b was initially found in transit data from TESS, and its confirmation using the NIRSpec instrument of the James Webb Space Telescope, which also observed its transmission spectrum, was published in January 2023.^[7] Another independent confirmation of the planet was published on arXiv in April 2023, and a year later accepted to the Astronomical Journal.^[3]

The JWST data is consistent with a featureless spectrum, as would be expected of a planet with no atmosphere, but is also consistent with some types of atmosphere, such as a thin carbon dioxide-dominated atmosphere like that of Mars, or an atmosphere obscured by a thick cloud deck such as that of Venus.^[4] Other atmospheric compositions, such as a methane-dominated atmosphere, are ruled out by this spectrum.^[6]

LHS 475 b is close in size to Earth, at 99% its diameter, but is much hotter, with an equilibrium temperature of 586 K (313 °C; 595 °F). Assuming the planet has little to no atmosphere, its dayside temperature is estimated at 748 K (475 °C; 887 °F). The planet completes an orbit around its star in just two days and is likely tidally locked.^[4]

The LHS 475 planetary system^[4]^[3]
Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	0.914±0.187^{[note 1]} $M$ _🜨	0.02037(37)	2.0291010(17)	0	87.38±0.19°	0.991±0.050 $R$ _🜨

Notes

^ The mass of this planet has not been measured; this value is an estimate.

References

^ "Finding the constellation which contains given sky coordinates". djm.cc. 2 August 2008.
^ ^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.
^ ^a ^b ^c ^d ^e ^f ^g ^h Ment, Kristo; Charbonneau, David; et al. (May 2024). "LHS 475 b: A Potential Venus Analog Orbiting a Nearby M Dwarf". The Astronomical Journal. 167 (5): 197. arXiv:2304.01920. Bibcode:2024AJ....167..197M. doi:10.3847/1538-3881/ad1b58.
^ ^a ^b ^c ^d ^e Lustig-Yaeger, J.; Fu, G.; et al. (January 2023). "A JWST transmission spectrum of the nearby Earth-sized exoplanet LHS 475 b". Nature Astronomy. 7 (11): 1317–1328. arXiv:2301.04191. Bibcode:2023NatAs...7.1317L. doi:10.1038/s41550-023-02064-z. S2CID 261439142.
^ "LHS 475". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 12 January 2023.
^ ^a ^b "NASA's Webb Confirms Its First Exoplanet". NASA. 11 January 2023. Retrieved 12 January 2023.
^ ^a ^b Chow, Denise (11 January 2023). "James Webb Telescope finds its first exoplanet - The planet is almost the same size as Earth, according to a research team led by astronomers at the Johns Hopkins University Applied Physics Laboratory". NBC News. Retrieved 12 January 2023.

[8] The mass of this planet has not been measured; this value is an estimate.

[constellation-1] "Finding the constellation which contains given sky coordinates". djm.cc. 2 August 2008.

[GaiaDR3-2] ^ ^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.

[Ment2023-3] ^ ^a ^b ^c ^d ^e ^f ^g ^h Ment, Kristo; Charbonneau, David; et al. (May 2024). "LHS 475 b: A Potential Venus Analog Orbiting a Nearby M Dwarf". The Astronomical Journal. 167 (5): 197. arXiv:2304.01920. Bibcode:2024AJ....167..197M. doi:10.3847/1538-3881/ad1b58.

[Lustig-Yaeger2023-4] Lustig-Yaeger, J.; Fu, G.; et al. (January 2023). "A JWST transmission spectrum of the nearby Earth-sized exoplanet LHS 475 b". Nature Astronomy. 7 (11): 1317–1328. arXiv:2301.04191. Bibcode:2023NatAs...7.1317L. doi:10.1038/s41550-023-02064-z. S2CID 261439142.

[SIMBAD-5] "LHS 475". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 12 January 2023.

[NASA20230111-6] "NASA's Webb Confirms Its First Exoplanet". NASA. 11 January 2023. Retrieved 12 January 2023.

[NBC-20230111-7] Chow, Denise (11 January 2023). "James Webb Telescope finds its first exoplanet - The planet is almost the same size as Earth, according to a research team led by astronomers at the Johns Hopkins University Applied Physics Laboratory". NBC News. Retrieved 12 January 2023.

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[note 1]