# 12 Hydrae

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Star in the constellation Hydra

12 Hydrae Location of 12 Hydrae (circled in red) Observation data Epoch J2000 Equinox J2000 Constellation Hydra[1] Right ascension 08h 46m 22.54441s[2] Declination −13° 32′ 51.8051″[2] Apparent magnitude (V) 4.32[1] Characteristics Evolutionary stage red giant branch[2] Spectral type G8 IIIb CN-1[3] B−V color index 0.900±0.015[1] Astrometry Radial velocity (Rv) −8.5±0.7[1] km/s Proper motion (μ) RA: +10.316[2] mas/yr Dec.: −15.012[2] mas/yr Parallax (π) 15.8840±0.3987 mas[2] Distance 205 ± 5 ly (63 ± 2 pc) Absolute magnitude (MV) +0.26[4] Orbit[5] Primary Aa Name 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 1.83[6] M☉ Radius 10.8[7] R☉ Luminosity 71[8] L☉ Surface gravity (log g) 3.13[6] cgs Temperature 5,105[7] K Metallicity [Fe/H] −0.01[6] dex Rotational velocity (v sin i) 4.6±0.2[4] km/s Age 410[2] Myr Other designations D Hya, 12 Hya, BD−13°2673, HD 74918, HIP 43067, HR 3484, SAO 154622, WDS J08464-1333[9] Database references SIMBAD data

**12 Hydrae** is a probable [astrometric binary](/source/Astrometric_binary)[10] [star](/source/Star) system located 205 [light years](/source/Light_year) away from the Sun in the [equatorial](/source/Celestial_equator) [constellation](/source/Constellation) of [Hydra](/source/Hydra_(constellation)). It has the [Bayer designation](/source/Bayer_designation) **D Hydrae**;[9] *12 Hydrae* is the [Flamsteed designation](/source/Flamsteed_designation). This system is visible to the naked eye as a faint, yellow-hued star with a combined [apparent visual magnitude](/source/Apparent_visual_magnitude) of 4.32.[1] It is moving closer to the Earth with a heliocentric [radial velocity](/source/Radial_velocity) of −8.5 km/s.[1]

This was found to be a double star by [R. A. Rossiter](/source/R._A._Rossiter) in 1953,[11] with the magnitude 13.7 companion having an [angular separation](/source/Angular_separation) of 26.8[″](/source/Second_of_arc) along a [position angle](/source/Position_angle) of 266°, as of 2016. The brighter, magnitude 4.32 component A is a [spectroscopic binary](/source/Spectroscopic_binary). As of 2009, the orbital solution for this pair is of low quality, giving a [period](/source/Orbital_period) of roughly 4 years and an [eccentricity](/source/Orbital_eccentricity) of around 0.4.[5]

The primary component is an aging [giant star](/source/Giant_star) with a [stellar classification](/source/Stellar_classification) of G8 IIIb CN-1,[3] where the suffix notation indicates an underabundance of the [cyanogen](/source/Cyanogen) molecule. It is 410 million years old[2] with 1.8 times the [mass of the Sun](/source/Mass_of_the_Sun).[6] After exhausting the hydrogen at its core and [evolving](/source/Stellar_evolution) off the [main sequence](/source/Main_sequence), the star has swollen to 11 times the [Sun's radius](/source/Sun's_radius).[7] It is radiating 71 times the [luminosity of the Sun](/source/Luminosity_of_the_Sun)[8] from its enlarged [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 5,105 [K](/source/Kelvin).[7]

## References

1. ^ [***a***](#cite_ref-Anderson2012_1-0) [***b***](#cite_ref-Anderson2012_1-1) [***c***](#cite_ref-Anderson2012_1-2) [***d***](#cite_ref-Anderson2012_1-3) [***e***](#cite_ref-Anderson2012_1-4) [***f***](#cite_ref-Anderson2012_1-5) Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", *Astronomy Letters*, **38** (5): 331, [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971), [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A), [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015), [S2CID](/source/S2CID_(identifier)) [119257644](https://api.semanticscholar.org/CorpusID:119257644).

1. ^ [***a***](#cite_ref-GaiaDR3_2-0) [***b***](#cite_ref-GaiaDR3_2-1) [***c***](#cite_ref-GaiaDR3_2-2) [***d***](#cite_ref-GaiaDR3_2-3) [***e***](#cite_ref-GaiaDR3_2-4) [***f***](#cite_ref-GaiaDR3_2-5) [***g***](#cite_ref-GaiaDR3_2-6) [***h***](#cite_ref-GaiaDR3_2-7) Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D5735066776630042112%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Keenan1989_3-0) [***b***](#cite_ref-Keenan1989_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, [Bibcode](/source/Bibcode_(identifier)):[1989ApJS...71..245K](https://ui.adsabs.harvard.edu/abs/1989ApJS...71..245K), [doi](/source/Doi_(identifier)):[10.1086/191373](https://doi.org/10.1086%2F191373)

1. ^ [***a***](#cite_ref-vonEiff2012_4-0) [***b***](#cite_ref-vonEiff2012_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, [arXiv](/source/ArXiv_(identifier)):[1204.2459](https://arxiv.org/abs/1204.2459), [Bibcode](/source/Bibcode_(identifier)):[2012A&A...542A.116A](https://ui.adsabs.harvard.edu/abs/2012A&A...542A.116A), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201118724](https://doi.org/10.1051%2F0004-6361%2F201118724), [S2CID](/source/S2CID_(identifier)) [53666672](https://api.semanticscholar.org/CorpusID:53666672).

1. ^ [***a***](#cite_ref-Hartkopf2006_5-0) [***b***](#cite_ref-Hartkopf2006_5-1) Hartkopf, W. I.; et al. (June 30, 2006), [*Sixth Catalog of Orbits of Visual Binary Stars*](https://web.archive.org/web/20170801102553/http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6), United States Naval Observatory, archived from [the original](http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6) on 2017-08-01, retrieved 2017-06-02.

1. ^ [***a***](#cite_ref-khalatyan2024_6-0) [***b***](#cite_ref-khalatyan2024_6-1) [***c***](#cite_ref-khalatyan2024_6-2) [***d***](#cite_ref-khalatyan2024_6-3) Khalatyan, A.; Anders, F.; Chiappini, C.; Queiroz, A. B. A.; Nepal, S.; Dal Ponte, M.; Jordi, C.; Guiglion, G.; Valentini, M.; Torralba Elipe, G.; Steinmetz, M.; Pantaleoni-González, M.; Malhotra, S.; Jiménez-Arranz, Ó.; Enke, H.; Casamiquela, L.; Ardèvol, J. (2024). "Transferring spectroscopic stellar labels to 217 million Gaia DR3 XP stars with SHBoost". *Astronomy and Astrophysics*. **691**: A98. [arXiv](/source/ArXiv_(identifier)):[2407.06963](https://arxiv.org/abs/2407.06963). [Bibcode](/source/Bibcode_(identifier)):[2024A&A...691A..98K](https://ui.adsabs.harvard.edu/abs/2024A&A...691A..98K). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202451427](https://doi.org/10.1051%2F0004-6361%2F202451427).

1. ^ [***a***](#cite_ref-tic_7-0) [***b***](#cite_ref-tic_7-1) [***c***](#cite_ref-tic_7-2) [***d***](#cite_ref-tic_7-3) Stassun, Keivan G.; et al. (2019). ["The Revised TESS Input Catalog and Candidate Target List"](https://doi.org/10.3847%2F1538-3881%2Fab3467). *The Astronomical Journal*. **158** (4): 138. [arXiv](/source/ArXiv_(identifier)):[1905.10694](https://arxiv.org/abs/1905.10694). [Bibcode](/source/Bibcode_(identifier)):[2019AJ....158..138S](https://ui.adsabs.harvard.edu/abs/2019AJ....158..138S). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/ab3467](https://doi.org/10.3847%2F1538-3881%2Fab3467).

1. ^ [***a***](#cite_ref-fetherolf2023_8-0) [***b***](#cite_ref-fetherolf2023_8-1) Fetherolf, Tara; Pepper, Joshua; Simpson, Emilie; Kane, Stephen R.; Močnik, Teo; English, John Edward; Antoci, Victoria; Huber, Daniel; Jenkins, Jon M.; Stassun, Keivan; Twicken, Joseph D.; Vanderspek, Roland; Winn, Joshua N. (2023). ["Variability Catalog of Stars Observed during the TESS Prime Mission"](https://doi.org/10.3847%2F1538-4365%2Facdee5). *The Astrophysical Journal Supplement Series*. **268** (1): 4. [arXiv](/source/ArXiv_(identifier)):[2208.11721](https://arxiv.org/abs/2208.11721). [Bibcode](/source/Bibcode_(identifier)):[2023ApJS..268....4F](https://ui.adsabs.harvard.edu/abs/2023ApJS..268....4F). [doi](/source/Doi_(identifier)):[10.3847/1538-4365/acdee5](https://doi.org/10.3847%2F1538-4365%2Facdee5).

1. ^ [***a***](#cite_ref-SIMBAD_9-0) [***b***](#cite_ref-SIMBAD_9-1) ["12 Hya"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=12+Hya). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved May 1, 2019.

1. **[^](#cite_ref-Eggleton2008_10-0)** Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", *[Monthly Notices of the Royal Astronomical Society](/source/Monthly_Notices_of_the_Royal_Astronomical_Society)*, **389** (2): 869–879, [arXiv](/source/ArXiv_(identifier)):[0806.2878](https://arxiv.org/abs/0806.2878), [Bibcode](/source/Bibcode_(identifier)):[2008MNRAS.389..869E](https://ui.adsabs.harvard.edu/abs/2008MNRAS.389..869E), [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2008.13596.x](https://doi.org/10.1111%2Fj.1365-2966.2008.13596.x), [S2CID](/source/S2CID_(identifier)) [14878976](https://api.semanticscholar.org/CorpusID:14878976).

1. **[^](#cite_ref-Rossiter1953_11-0)** 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](/source/Bibcode_(identifier)):[1953AJ.....58...29R](https://ui.adsabs.harvard.edu/abs/1953AJ.....58...29R), [doi](/source/Doi_(identifier)):[10.1086/106804](https://doi.org/10.1086%2F106804).

v t e Constellation of Hydra List of stars in Hydra Hydra in Chinese astronomy Stars Bayer α (Alphard) β γ (Naga) δ ε (Ashlesha) ζ η θ ι (Ukdah) κ λ μ ν ξ ο π ρ σ (Minchir) τ1 τ2 υ1 (Zhang) υ2 φ1 φ2 φ3 χ1 χ2 ψ ω b1 b3 C F Flamsteed 1 2 3 6 (a) 9 10 12 (D) 14 15 17 19 20 21 23 24 25 26 27 (P) 28 29 33 (A) 34 37 44 47 48 50 51 (k) 52 (l) 54 (m) 55 56 57 58 (Solitaire) 59 60 10 Crt 17 Crt 20 Crt 2 Sex Variable R U V W TW EX HS KU LQ V361 V419 V421 V478 V484 HR 3378 3538 3749 (G) 3750 3858 (I) 3862 3919 3923 (Felis) 4162 4328 4339 (β Ant) 4445 5265 HD 72659 74156 82943 86226 86264 90156 (γ Ant) Other 2MASS 1114−2618 ESO 439-26 Gliese 328 Gliese 357 Gliese 433 Gliese 453 GJ 3634 HAT-P-30 HE 1256−2738 HE 1327−2326 LHS 2065 LHS 3003 LTT 3780 SDSS J090745.0+024507 WASP-25 WASP-36 WASP-84 WASP-166 (Filetdor) WISE 0855−0714 WISEA J1141−3326 Exoplanets Gliese 357 d HD 72659 b HD 74156 b c HD 82943 b c HD 86226 b HD 86264 b TW Hydrae b (unconfirmed) WASP-193b Star clusters Messier 48 Messier 68 NGC 5694 Price-Whelan 1 Nebulae Abell 33 Abell 35 NGC 3242 Southern Owl Nebula Galaxies Messier 83 NGC 2617 2642 2697 2708 2758 2835 2848 2865 2890 2935 2936 2937 2960 2962 2986 2992 3030 3052 3054 3081 3109 3124 3200 3285 3285B 3290 3305 3307 3308 3309 3311 3312 3313 3314 3315 3316 3336 3369 3383 3393 3402 3463 3464 3585 3621 3673 3717 3904 3923 3936 4980 4993 5042 5061 5078 5085 5101 5135 5260 5264 5495 5626 Other 3C 196.1 AM 1316−241 Arp 7 CTQ 327 ESO 510-G13 GAMA202627 GLEAM J0917−0012 Hydra A IC 535 MRC 1138−262 Peekaboo Galaxy PKS 1151−348 RX J0911.4+0551 SDSS J0841+0101 TN J0924−2201 Tololo 1247−232 ZwCl 1693 BCG Galaxy clusters Abell 754 Abell 3411 Abell 3412 Bullet Group Hickson 40 Astronomical events GW170817 Category

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Adapted from the Wikipedia article [12 Hydrae](https://en.wikipedia.org/wiki/12_Hydrae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/12_Hydrae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.