# Beta Hydrae

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Double star in the constellation Hydra

β Hydrae Location of β Hydrae (circled) Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) Constellation Hydra[1] Right ascension 11h 52m 54.52149s[2] Declination −33° 54′ 29.2672″[2] Apparent magnitude (V) 4.29 (combined)[1] (4.67 + 5.47)[3] Characteristics Spectral type B9IIIp Si[4] + ? kB8hB8HeA0VSi[5] U−B color index −0.34[1] B−V color index −0.100±0.003[1] R−I color index −0.08[6] Variable type α2 CVn[7] Astrometry Radial velocity (Rv) −1.0±3.7[1] km/s Proper motion (μ) RA: −56.56[2] mas/yr Dec.: +0.19[2] mas/yr Parallax (π) 10.53±0.60 mas[2] Distance 310 ± 20 ly (95 ± 5 pc) Absolute magnitude (MV) −0.59[1] Details A Mass 3.36±0.15[8] M☉ Radius 3.89±0.08[9] R☉ Luminosity 257+45 −38[10] L☉ Surface gravity (log g) 2.52±0.03[9] cgs Temperature 10,980±110[9] K Rotation 2.35666±0.00002 d[11] Age 178+62 −12[10] Myr B Mass ~3[12] M☉ Other designations Beta Hydrae, Beta Hya, HJ 4478AB, β Hya, CD−33°8018, CPD−33°3159, GC 16258, HD 103192, HIP 57936, HR 4552, SAO 202901, PPM 289465, CCDM J11529-3354AB, WDS 11529-3354AB[13] Database references SIMBAD data A B

[light curve](/source/Light_curve) for Beta Hydrae plotted from *[TESS](/source/Transiting_Exoplanet_Survey_Satellite)* data[14]

**Beta Hydrae**, Latinized from **β Hydrae**, is a [double](/source/Double_star) [star](/source/Star) in the [equatorial](/source/Celestial_equator) [constellation](/source/Constellation) of [Hydra](/source/Hydra_(constellation)).[13] Historically, Beta Hydrae was designated **28 Crateris**, but the latter fell out of use when the [IAU](/source/International_Astronomical_Union) defined the permanent constellation boundaries in 1930.[15] The system is faintly visible to the naked eye with a combined [apparent visual magnitude](/source/Apparent_visual_magnitude) that ranges around 4.29.[1] It is located at a distance of approximately 310 [light years](/source/Light_year) from the [Sun](/source/Sun) based on [parallax](/source/Stellar_parallax).

The double nature of this system was first reported by English astronomer [John Herschel](/source/John_Herschel) in 1834.[16] The brighter primary, designated component A, has an average visual magnitude of 4.67, while the secondary, component B, is of magnitude 5.47. As of 2002, the secondary is located at an [angular separation](/source/Angular_separation) of 0.65 [arcseconds](/source/Arcseconds) from the primary, along a [position angle](/source/Position_angle) of 28.5°.[3]

The brighter component is an [α2 Canum Venaticorum variable](/source/Alpha2_Canum_Venaticorum_variable) that changes in brightness with a period of 2.344 days and an amplitude of 0.04 in visual magnitude.[7] It is a [magnetic](/source/Stellar_magnetic_field) [chemically-peculiar star](/source/Chemically-peculiar_star)[17] with an average quadratic field strength of (−206±68)×10−4 [T](/source/Tesla_(unit)).[11] The star is around 178 million years old[10] with 3.4[8] times the [mass of the Sun](/source/Mass_of_the_Sun) and 3.9[9] times the [Sun's radius](/source/Sun's_radius). On average, it is radiating 257[10] times the [luminosity of the Sun](/source/Luminosity_of_the_Sun) from its [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 10,980 K.[9]

In 1972, M. R. Molnar found a [stellar classification](/source/Stellar_classification) of B9IIIp Si for β Hydrae A, showing an abundance anomaly for silicon.[4] R. F. Garrison and R. O. Gray assigned it a class of kB8hB8HeA0VSi in 1994.[5] This notation indicates the [Calcium K line](/source/Calcium_K_line) matches a star of class B8, the [hydrogen lines](/source/Hydrogen_lines) also match a B8 [spectrum](/source/Stellar_spectrum), while the helium lines match an [A-type main-sequence star](/source/A-type_main-sequence_star) of class A0V.[18] They noted that the hydrogen lines have "curious rounded profiles".[5] Later studies list abundance anomalies of silicon, chromium, and strontium.[19]

## Cultural significance

The [Kalapalo people](/source/Kalapalo_people) of [Mato Grosso](/source/Mato_Grosso) state in Brazil called β Hydrae and [ψ Hya](/source/Psi_Hydrae) *Kafanifani*.[20]

## References

1. ^ [***a***](#cite_ref-Anderson_Francis_2012_1-0) [***b***](#cite_ref-Anderson_Francis_2012_1-1) [***c***](#cite_ref-Anderson_Francis_2012_1-2) [***d***](#cite_ref-Anderson_Francis_2012_1-3) [***e***](#cite_ref-Anderson_Francis_2012_1-4) [***f***](#cite_ref-Anderson_Francis_2012_1-5) [***g***](#cite_ref-Anderson_Francis_2012_1-6) Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". *[Astronomy Letters](/source/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). [XHIP record for this object](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-ref=VIZ681510a8389ecb&-out.src=V%2F137D%2FXHIP&-nav=cat%3AV%2F137D%26tab%3A{V%2F137D%2FXHIP}%26key%3Asource%3DV%2F137D%2FXHIP%26HTTPPRM%3A&-source=V%2F137D%2FXHIP&-out=HIP&HIP=57936&-out=Comp&-out=Gr&-out=RAJ2000&-out=DEJ2000&-out=Dist&-out=X&-out=Y&-out=Z&-out=SpType&-out=Simbad&-out=Hpmag&-out=Lum&-out=Cst) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-vanLeeuwen2007_2-0) [***b***](#cite_ref-vanLeeuwen2007_2-1) [***c***](#cite_ref-vanLeeuwen2007_2-2) [***d***](#cite_ref-vanLeeuwen2007_2-3) [***e***](#cite_ref-vanLeeuwen2007_2-4) van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", *Astronomy and Astrophysics*, **474** (2): 653–664, [arXiv](/source/ArXiv_(identifier)):[0708.1752](https://arxiv.org/abs/0708.1752), [Bibcode](/source/Bibcode_(identifier)):[2007A&A...474..653V](https://ui.adsabs.harvard.edu/abs/2007A&A...474..653V), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078357](https://doi.org/10.1051%2F0004-6361%3A20078357), [S2CID](/source/S2CID_(identifier)) [18759600](https://api.semanticscholar.org/CorpusID:18759600)

1. ^ [***a***](#cite_ref-Fabricius_et_al_2002_3-0) [***b***](#cite_ref-Fabricius_et_al_2002_3-1) Fabricius, C.; et al. (2002). ["The Tycho double star catalogue"](https://doi.org/10.1051%2F0004-6361%3A20011822). *Astronomy and Astrophysics*. **384**: 180–189. [Bibcode](/source/Bibcode_(identifier)):[2002A&A...384..180F](https://ui.adsabs.harvard.edu/abs/2002A&A...384..180F). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20011822](https://doi.org/10.1051%2F0004-6361%3A20011822).

1. ^ [***a***](#cite_ref-Molnar1972_4-0) [***b***](#cite_ref-Molnar1972_4-1) Molnar, Michael R. (July 1972). "The Helium-Weak Stars". *Astrophysical Journal*. **175**: 453. [Bibcode](/source/Bibcode_(identifier)):[1972ApJ...175..453M](https://ui.adsabs.harvard.edu/abs/1972ApJ...175..453M). [doi](/source/Doi_(identifier)):[10.1086/151570](https://doi.org/10.1086%2F151570).

1. ^ [***a***](#cite_ref-Garrison_Gray_1994_5-0) [***b***](#cite_ref-Garrison_Gray_1994_5-1) [***c***](#cite_ref-Garrison_Gray_1994_5-2) Garrison, R. F.; Gray, R. O. (April 1994). "The late B-type stars: refined MK classification, confrontation with Stromgren photometry, and the effects of rotation". *Astronomical Journal*. **107**: 1556. [Bibcode](/source/Bibcode_(identifier)):[1994AJ....107.1556G](https://ui.adsabs.harvard.edu/abs/1994AJ....107.1556G). [doi](/source/Doi_(identifier)):[10.1086/116967](https://doi.org/10.1086%2F116967).

1. **[^](#cite_ref-bsc1_6-0)** Hoffleit, D.; Warren, Jr., W. H. ["HR 4552, database entry"](http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=V/50/catalog&recno=4552). *The Bright Star Catalogue* (5th Revised (Preliminary Version) ed.). [Centre de Données astronomiques de Strasbourg](/source/Centre_de_Donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2020-12-31. ID [V/50](http://vizier.u-strasbg.fr/viz-bin/Cat?V/50). Accessed on line September 23, 2008.

1. ^ [***a***](#cite_ref-Samus_et_al_2017_7-0) [***b***](#cite_ref-Samus_et_al_2017_7-1) Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". *Astronomy Reports*. **61** (1): 80. [Bibcode](/source/Bibcode_(identifier)):[2017ARep...61...80S](https://ui.adsabs.harvard.edu/abs/2017ARep...61...80S). [doi](/source/Doi_(identifier)):[10.1134/S1063772917010085](https://doi.org/10.1134%2FS1063772917010085). [S2CID](/source/S2CID_(identifier)) [125853869](https://api.semanticscholar.org/CorpusID:125853869).

1. ^ [***a***](#cite_ref-aaa334_181_8-0) [***b***](#cite_ref-aaa334_181_8-1) North, P. (June 1998). "Do SI stars undergo any rotational braking?". *Astronomy and Astrophysics*. **334**: 181–187. [arXiv](/source/ArXiv_(identifier)):[astro-ph/9802286](https://arxiv.org/abs/astro-ph/9802286). [Bibcode](/source/Bibcode_(identifier)):[1998A&A...334..181N](https://ui.adsabs.harvard.edu/abs/1998A&A...334..181N).

1. ^ [***a***](#cite_ref-Arcos_et_al_2018_9-0) [***b***](#cite_ref-Arcos_et_al_2018_9-1) [***c***](#cite_ref-Arcos_et_al_2018_9-2) [***d***](#cite_ref-Arcos_et_al_2018_9-3) [***e***](#cite_ref-Arcos_et_al_2018_9-4) Arcos, C.; Kanaan, S.; Chávez, J.; Vanzi, L.; Araya, I.; Curé, M. (March 2018). ["Stellar parameters and H α line profile variability of Be stars in the BeSOS survey"](https://doi.org/10.1093%2Fmnras%2Fstx3075). *Monthly Notices of the Royal Astronomical Society*. **474** (4): 5287–5299. [arXiv](/source/ArXiv_(identifier)):[1711.08675](https://arxiv.org/abs/1711.08675). [Bibcode](/source/Bibcode_(identifier)):[2018MNRAS.474.5287A](https://ui.adsabs.harvard.edu/abs/2018MNRAS.474.5287A). [doi](/source/Doi_(identifier)):[10.1093/mnras/stx3075](https://doi.org/10.1093%2Fmnras%2Fstx3075).

1. ^ [***a***](#cite_ref-Sikora_et_al_2019_10-0) [***b***](#cite_ref-Sikora_et_al_2019_10-1) [***c***](#cite_ref-Sikora_et_al_2019_10-2) [***d***](#cite_ref-Sikora_et_al_2019_10-3) Sikora, J.; et al. (February 2019). ["A volume-limited survey of mCP stars within 100 pc - I. Fundamental parameters and chemical abundances"](https://doi.org/10.1093%2Fmnras%2Fsty3105). *Monthly Notices of the Royal Astronomical Society*. **483** (2): 2300–2324. [arXiv](/source/ArXiv_(identifier)):[1811.05633](https://arxiv.org/abs/1811.05633). [Bibcode](/source/Bibcode_(identifier)):[2019MNRAS.483.2300S](https://ui.adsabs.harvard.edu/abs/2019MNRAS.483.2300S). [doi](/source/Doi_(identifier)):[10.1093/mnras/sty3105](https://doi.org/10.1093%2Fmnras%2Fsty3105).

1. ^ [***a***](#cite_ref-Sikora_et_al_2019b_11-0) [***b***](#cite_ref-Sikora_et_al_2019b_11-1) Sikora, J.; et al. (March 2019). ["A volume-limited survey of mCP stars within 100 pc II: rotational and magnetic properties"](https://doi.org/10.1093%2Fmnras%2Fsty2895). *Monthly Notices of the Royal Astronomical Society*. **483** (3): 3127–3145. [arXiv](/source/ArXiv_(identifier)):[1811.05635](https://arxiv.org/abs/1811.05635). [Bibcode](/source/Bibcode_(identifier)):[2019MNRAS.483.3127S](https://ui.adsabs.harvard.edu/abs/2019MNRAS.483.3127S). [doi](/source/Doi_(identifier)):[10.1093/mnras/sty2895](https://doi.org/10.1093%2Fmnras%2Fsty2895).

1. **[^](#cite_ref-kaler_12-0)** Kaler, James B. (July 4, 2015). ["Beta Hydrae"](http://stars.astro.illinois.edu/sow/betahya.html). *Stars*. Retrieved 2020-12-31.

1. ^ [***a***](#cite_ref-SIMBAD_13-0) [***b***](#cite_ref-SIMBAD_13-1) ["bet hya"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=bet+hya). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2020-12-31.

1. **[^](#cite_ref-MAST_14-0)** ["MAST: Barbara A. Mikulski Archive for Space Telescopes"](https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html). Space Telescope Science Institute. Retrieved 8 December 2021.

1. **[^](#cite_ref-Wagman1987_15-0)** Wagman, M. (August 1987). "Flamsteed's Missing Stars". *Journal for the History of Astronomy*. **18** (3): 216. [Bibcode](/source/Bibcode_(identifier)):[1987JHA....18..209W](https://ui.adsabs.harvard.edu/abs/1987JHA....18..209W). [doi](/source/Doi_(identifier)):[10.1177/002182868701800305](https://doi.org/10.1177%2F002182868701800305). [S2CID](/source/S2CID_(identifier)) [118445625](https://api.semanticscholar.org/CorpusID:118445625).

1. **[^](#cite_ref-Mason_et_al_2014_16-0)** Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", *The Astronomical Journal*, **122** (6): 3466–3471, [Bibcode](/source/Bibcode_(identifier)):[2001AJ....122.3466M](https://ui.adsabs.harvard.edu/abs/2001AJ....122.3466M), [doi](/source/Doi_(identifier)):[10.1086/323920](https://doi.org/10.1086%2F323920).

1. **[^](#cite_ref-Bychkov_et_al_2003_17-0)** Bychkov, V. D.; et al. (August 2003). "Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars". *Astronomy and Astrophysics*. **407** (2): 631–642. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0307356](https://arxiv.org/abs/astro-ph/0307356). [Bibcode](/source/Bibcode_(identifier)):[2003A&A...407..631B](https://ui.adsabs.harvard.edu/abs/2003A&A...407..631B). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20030741](https://doi.org/10.1051%2F0004-6361%3A20030741). [S2CID](/source/S2CID_(identifier)) [14184105](https://api.semanticscholar.org/CorpusID:14184105).

1. **[^](#cite_ref-Gray_Corbally_2009_18-0)** Gray, Richard O.; Corbally, Christopher J. (2009). *Stellar Spectral Classification*. [Princeton University Press](/source/Princeton_University_Press). pp. 176–183. [ISBN](/source/ISBN_(identifier)) [978-0691125114](https://en.wikipedia.org/wiki/Special:BookSources/978-0691125114).

1. **[^](#cite_ref-Mikulášek2007_19-0)** Mikulášek, Z.; et al. (January 2007). ["On-line database of photometric observations of magnetic chemically peculiar stars"](https://doi.org/10.1002%2Fasna.200610705). *Astronomische Nachrichten*. **328** (1): 10–15. [Bibcode](/source/Bibcode_(identifier)):[2007AN....328...10M](https://ui.adsabs.harvard.edu/abs/2007AN....328...10M). [doi](/source/Doi_(identifier)):[10.1002/asna.200610705](https://doi.org/10.1002%2Fasna.200610705).

1. **[^](#cite_ref-basso87_20-0)** Basso, Ellen B. (1987). [*In Favor of Deceit: A Study of Tricksters in an Amazonian Society*](https://archive.org/details/infavorofdeceits0000bass). Tucson, Arizona: University of Arizona Press. p. [360](https://archive.org/details/infavorofdeceits0000bass/page/360). [ISBN](/source/ISBN_(identifier)) [0-8165-1022-9](https://en.wikipedia.org/wiki/Special:BookSources/0-8165-1022-9).

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 [Beta Hydrae](https://en.wikipedia.org/wiki/Beta_Hydrae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Beta_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.