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HD 90156
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Hydra
Right ascension	10h 23m 55.274s
Declination	–29° 38′ 43.91″
Apparent magnitude (V)	6.92
Characteristics
Spectral type	G5 V
Apparent magnitude (B)	7.579
Apparent magnitude (J)	5.685±0.023
Apparent magnitude (H)	5.382±0.034
Apparent magnitude (K)	5.245±0.024
B−V color index	0.659±0.007
Variable type	None
Astrometry
Radial velocity (Rv)	26.958±0.0002 km/s
Proper motion (μ)	RA: –39.159 mas/yr ; Dec.: 99.302 mas/yr
Parallax (π)	45.5628 ± 0.0214 mas
Distance	71.58 ± 0.03 ly ; (21.95 ± 0.01 pc)
Absolute magnitude (MV)	5.17
Details
Mass	0.837±0.009 M☉
Radius	0.876±0.013 R☉
Luminosity	0.74±0.01 L☉
Surface gravity (log g)	4.40±0.02 cgs
Temperature	5,599±12 K
Metallicity [Fe/H]	–0.24±0.01 dex
Rotational velocity (v sin i)	0.817 km/s
Age	4.4 Gyr; 8.1±3.8 Gyr
Other designations
	Gamma Antliae, CD–29° 8316, GJ 3597, HD 90156, HIP 50921, SAO 178771, PPM 257610
Database references
SIMBAD	data
Exoplanet Archive	data

HD 90156 is a star with an orbiting exoplanet in the constellation Hydra. Based on parallax measurements, it is located at a distance of 71.6 light years from the Sun.^[2] The system is drifting further away with a heliocentric radial velocity of 27 km/s.^[5] The apparent visual magnitude of this star is 6.92,^[1] which is places it near the lower limit of visibility to the naked eye. A survey in 2015 ruled out the existence of any stellar companions at projected distances above 5 AU.^[10]

This star was designated as Gamma Antliae by Lacaille, and Gould intended to keep it in the Antlia constellation. However, the delineating of constellation boundaries in 1930 saw it transferred to Hydra.^[11]

The spectrum of HD 90156 presents as a G-type main-sequence star with a stellar classification of G5 V^[3] It is rotating slowly with a projected rotational velocity of 0.817,^[8] and it only displays a low level of magnetic activity in its chromosphere. The metallicity of the star is lower than in the Sun, indicating a paucity of elements with mass greater than helium.^[4] The star has 84% of the mass of the Sun and 88% of the Sun's radius. It is radiating 74%^[7] of the Sun's luminosity from its photosphere at an effective temperature of 5,599 km/s.^[4]

Planetary system

In 2011, an exoplanet was found in an eccentric orbit around the host star using Doppler spectroscopy. As the inclination of its orbital plane is unknown, only a lower bound on its mass can be determined. It has at least 18 times the mass of the Earth. The exoplanet is orbiting its host star with a separation of 0.25 AU and a period of 50 days.^[4]

The HD 90156 planetary system^[4]
Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥17.98 ± 1.46 $M$ _🜨	0.250 ± 0.004	49.77 ± 0.07	0.31 ± 0.10	—	—

References

^ ^a ^b ^c ^d ^e ^f ^g ^h Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
^ ^a ^b ^c ^d ^e 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 Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
^ ^a ^b ^c ^d ^e ^f ^g ^h Mordasini, C.; et al. (2011). "The HARPS search for southern extrasolar planets XXIV. Companions to HD 85390, HD 90156, and HD 103197: a Neptune analog and two intermediate-mass planets". Astronomy and Astrophysics. 526. A111. arXiv:1010.0856. Bibcode:2011A&A...526A.111M. doi:10.1051/0004-6361/200913521. S2CID 59062607.
^ ^a ^b Soubiran, C.; et al. (2018). "Gaia Data Release 2. The catalogue of radial velocity standard stars". Astronomy and Astrophysics. 616: A7. arXiv:1804.09370. Bibcode:2018A&A...616A...7S. doi:10.1051/0004-6361/201832795. S2CID 52952408.
^ ^a ^b ^c Gomes da Silva, J.; Santos, N. C.; Adibekyan, V.; Sousa, S. G.; Campante, T. L.; Figueira, P.; Bossini, D.; Delgado-Mena, E.; Monteiro, M. J. P. F. G.; de Laverny, P.; Recio-Blanco, A.; Lovis, C. (February 2021). "Stellar chromospheric activity of 1674 FGK stars from the AMBRE-HARPS sample. I. A catalogue of homogeneous chromospheric activity". Astronomy & Astrophysics. 646: A77. arXiv:2012.10199. Bibcode:2021A&A...646A..77G. doi:10.1051/0004-6361/202039765. eISSN 1432-0746. ISSN 0004-6361. S2CID 229331727.
^ ^a ^b Bonfanti, A.; Ortolani, S.; Nascimbeni, V. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics. 585: 14. arXiv:1511.01744. Bibcode:2016A&A...585A...5B. doi:10.1051/0004-6361/201527297. S2CID 53971692. A5.
^ ^a ^b ^c Costa Silva, A. R.; et al. (February 2020). "Chemical abundances of 1111 FGK stars from the HARPS-GTO planet search sample. III. Sulfur". Astronomy & Astrophysics. 634: 10. arXiv:1912.08659. Bibcode:2020A&A...634A.136C. doi:10.1051/0004-6361/201936523. S2CID 209405391. A136.
^ "HD 90156". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2023-12-20.
^ Mugrauer, M.; Ginski, C. (12 May 2015). "High-contrast imaging search for stellar and substellar companions of exoplanet host stars". Monthly Notices of the Royal Astronomical Society. 450 (3): 3127–3136. Bibcode:2015MNRAS.450.3127M. doi:10.1093/mnras/stv771. hdl:1887/49340.
^ Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, VA: The McDonald & Woodward Publishing Company. p. 29. ISBN 978-0-939923-78-6.