Astronomy:12 Hydrae
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| 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 |
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]
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
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 3.0 3.1 Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series 71: 245, doi:10.1086/191373, Bibcode: 1989ApJS...71..245K
- ↑ 4.0 4.1 Ammler-von Eiff, Matthias; Reiners, Ansgar (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, doi:10.1051/0004-6361/201118724, Bibcode: 2012A&A...542A.116A.
- ↑ 5.0 5.1 Hartkopf, W. I. et al. (June 30, 2006), Sixth Catalog of Orbits of Visual Binary Stars, United States Naval Observatory, http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6, retrieved 2017-06-02.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal 150 (3): 88, doi:10.1088/0004-6256/150/3/88, Bibcode: 2015AJ....150...88L.
- ↑ 7.0 7.1 "12 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=12+Hya.
- ↑ 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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E.
- ↑ 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, doi:10.1086/106804, Bibcode: 1953AJ.....58...29R.
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