12 Hydrae
12 Hydrae is a probable astrometric binary[8] star system located 202 light years away from the Sun in the equatorial constellation of Hydra. It has the Bayer designation D Hydrae;[7] 12 Hydrae is the Flamsteed designation. This system is visible to the naked eye as a faint, yellow-hued star with a combined apparent visual magnitude of 4.32.[2] It is moving closer to the Earth with a heliocentric radial velocity of −8.5 km/s.[2]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 08h 46m 22.53544s[1] |
| Declination | −13° 32′ 51.7502″[1] |
| Apparent magnitude (V) | 4.32[2] |
| Characteristics | |
| Spectral type | G8 IIIb CN-1[3] |
| B−V color index | 0.900±0.015[2] |
| Astrometry | |
| Radial velocity (Rv) | −8.5±0.7[2] km/s |
| Proper motion (μ) | RA: +18.789[1] mas/yr Dec.: −18.385[1] mas/yr |
| Parallax (π) | 16.1839 ± 0.6646[1] mas |
| Distance | 202 ± 8 ly (62 ± 3 pc) |
| Absolute magnitude (MV) | +0.26[4] |
| Orbit[5] | |
| Primary | Aa |
| Companion | Ab |
| Period (P) | 1,592±806 d |
| Semi-major axis (a) | 0.0116±0.057″ |
| Eccentricity (e) | 0.40±0.26 |
| Inclination (i) | 58±10° |
| Longitude of the node (Ω) | 91±16° |
| Periastron epoch (T) | 49,194±664 |
| Argument of periastron (ω) (secondary) | 103±34° |
| Details | |
| Mass | 2.32[6] M☉ |
| Radius | 11.51+0.18 −0.37[1] R☉ |
| Luminosity | 77.468±3.553[1] L☉ |
| Temperature | 4,968±13[6] K |
| Rotational velocity (v sin i) | 4.6±0.2[4] km/s |
| Age | 910[6] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
This was found to be a double star by R. A. Rossiter in 1953,[9] with the magnitude 13.7 companion having an angular separation of 26.8″ along a position angle of 266°, as of 2016. The brighter, magnitude 4.32 component A is a spectroscopic binary. As of 2009, the orbital solution for this pair is of low quality, giving a period of roughly 4 years and an eccentricity of around 0.4.[5]
The primary component is an aging giant star with a stellar classification of G8 IIIb CN-1,[3] where the suffix notation indicates an underabundance of the cyanogen molecule. It is 910[6] million years old with 2.32[6] times the mass of the Sun. After exhausting the hydrogen at its core and evolving off the main sequence, the star has swollen to 11.5[1] times the Sun's radius. It is radiating 77[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,968 K.[6]
References
- Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- 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.
- Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373
- Ammler-von Eiff, M.; Reiners, A. (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724.
- Hartkopf, W. I.; et al. (June 30, 2006), Sixth Catalog of Orbits of Visual Binary Stars, United States Naval Observatory, retrieved 2017-06-02.
- Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal, 150 (3), 88, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88.
- "12 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved May 1, 2019.
- Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
- Rossiter, R. A. (February 1953), "Seventh list of new Southern double stars found at the Lamont-Hussey Observatory of the University of Michigan at Bloemfontein, South Africa.", Astronomical Journal, 58: 29–30, Bibcode:1953AJ.....58...29R, doi:10.1086/106804.