# HD 83953

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Star in the constellation Hydra

This article is about I (upper case "i") Hydrae; not to be confused with [l (lower case "L") Hydrae](/source/L_Hydrae) or [ι (iota) Hydrae](/source/Iota_Hydrae).

HD 83953 Location of HD 83953 (circled in red) Observation data Epoch J2000 Equinox J2000 Constellation Hydra[1] Right ascension 09h 41m 17.00785s[2] Declination −23° 35′ 29.4325″[2] Apparent magnitude (V) 4.76[1] Characteristics Evolutionary stage main sequence[3] Spectral type B5 V[4] B−V color index −0.117±0.015[1] Astrometry Radial velocity (Rv) +16.05±1.5[5] km/s Proper motion (μ) RA: −29.969[2] mas/yr Dec.: +1.914[2] mas/yr Parallax (π) 6.5733±0.2851 mas[2] Distance 500 ± 20 ly (152 ± 7 pc) Absolute magnitude (MV) −1.19[1] Details Mass 4.57±0.08[6] M☉ Radius 4.00±0.08[7] R☉ Luminosity 708+60 −55[6] L☉ Surface gravity (log g) 2.54±0.03[7] cgs Temperature 15,000±150[7] K Rotational velocity (v sin i) 315[6][8] km/s Other designations I Hya, BD−22°2684, HD 83953, HIP 47522, HR 3858, SAO 177840[9] Database references SIMBAD data

**HD 83953** (**I Hydrae**) is a single,[10] blue-white hued [star](/source/Star) in the equatorial [constellation](/source/Constellation) of [Hydra](/source/Hydra_(constellation)). It is visible to the naked eye, having an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 4.76.[1] Based upon an annual [parallax shift](/source/Stellar_parallax) of 6.6 [mas](/source/Milliarcsecond),[2] the distance to this star is estimated as 500 [light years](/source/Light_year). It is moving further from Earth with a heliocentric [radial velocity](/source/Radial_velocity) of +16 km/s.[5]

This is a [B-type main-sequence star](/source/B-type_main-sequence_star) with a [stellar classification](/source/Stellar_classification) of B5 V.[4] It has been known to be a [Be star](/source/Be_star) since 1926, when an [Hβ](/source/Hydrogen_spectral_series) [emission line](/source/Emission_line) was discovered in the [stellar spectrum](/source/Stellar_spectrum) by [Mount Wilson Observatory](/source/Mount_Wilson_Observatory).[11] This energy is coming from a circumstellar envelope of heated gas that has been expelled from the central star and formed a thin orbiting disk.[12] HD 83953 is spinning rapidly with a [projected rotational velocity](/source/Projected_rotational_velocity) of 315 km/s, giving the star an [oblate shape](/source/Oblate_spheroid) with an [equatorial bulge](/source/Equatorial_bulge) that is 18% larger than the polar radius.[8]

HD 83953 has 4.6[6] times the [mass of the Sun](/source/Mass_of_the_Sun) and 4.0[7] times the [Sun's radius](/source/Sun's_radius). It is radiating 708[6] times the [Sun's luminosity](/source/Sun's_luminosity) from its [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 15,000 K.[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) 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=47522&-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-GaiaDR2_2-0) [***b***](#cite_ref-GaiaDR2_2-1) [***c***](#cite_ref-GaiaDR2_2-2) [***d***](#cite_ref-GaiaDR2_2-3) [***e***](#cite_ref-GaiaDR2_2-4) [***f***](#cite_ref-GaiaDR2_2-5) [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. ([Gaia collaboration](/source/Data_Processing_and_Analysis_Consortium)) (August 2018). ["*Gaia* Data Release 2: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F201833051). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **616**. A1. [arXiv](/source/ArXiv_(identifier)):[1804.09365](https://arxiv.org/abs/1804.09365). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...1G](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833051](https://doi.org/10.1051%2F0004-6361%2F201833051).

1. **[^](#cite_ref-zorec2016_3-0)** Zorec, J.; Frémat, Y.; Domiciano De Souza, A.; Royer, F.; Cidale, L.; Hubert, A.-M.; Semaan, T.; Martayan, C.; Cochetti, Y. R.; Arias, M. L.; Aidelman, Y.; Stee, P. (2016). "Critical study of the distribution of rotational velocities of be stars. I. Deconvolution methods, effects due to gravity darkening, macroturbulence, and binarity". *Astronomy and Astrophysics*. **595**: A132. [Bibcode](/source/Bibcode_(identifier)):[2016A&A...595A.132Z](https://ui.adsabs.harvard.edu/abs/2016A&A...595A.132Z). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201628760](https://doi.org/10.1051%2F0004-6361%2F201628760). [hdl](/source/Hdl_(identifier)):[11336/37946](https://hdl.handle.net/11336%2F37946).

1. ^ [***a***](#cite_ref-houk1978_4-0) [***b***](#cite_ref-houk1978_4-1) Houk, Nancy; Smith-Moore, M. (1978), *Michigan catalogue of two-dimensional spectral types for the HD stars*, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, [Bibcode](/source/Bibcode_(identifier)):[1988mcts.book.....H](https://ui.adsabs.harvard.edu/abs/1988mcts.book.....H).

1. ^ [***a***](#cite_ref-Becker2015_5-0) [***b***](#cite_ref-Becker2015_5-1) Becker, Juliette C.; et al. (April 2015), "Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra", *The Astrophysical Journal Supplement Series*, **217** (2): 13, [arXiv](/source/ArXiv_(identifier)):[1503.03874](https://arxiv.org/abs/1503.03874), [Bibcode](/source/Bibcode_(identifier)):[2015ApJS..217...29B](https://ui.adsabs.harvard.edu/abs/2015ApJS..217...29B), [doi](/source/Doi_(identifier)):[10.1088/0067-0049/217/2/29](https://doi.org/10.1088%2F0067-0049%2F217%2F2%2F29), [S2CID](/source/S2CID_(identifier)) [33968873](https://api.semanticscholar.org/CorpusID:33968873), 29.

1. ^ [***a***](#cite_ref-zorec2012_6-0) [***b***](#cite_ref-zorec2012_6-1) [***c***](#cite_ref-zorec2012_6-2) [***d***](#cite_ref-zorec2012_6-3) [***e***](#cite_ref-zorec2012_6-4) Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", *Astronomy & Astrophysics*, **537**: A120, [arXiv](/source/ArXiv_(identifier)):[1201.2052](https://arxiv.org/abs/1201.2052), [Bibcode](/source/Bibcode_(identifier)):[2012A&A...537A.120Z](https://ui.adsabs.harvard.edu/abs/2012A&A...537A.120Z), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201117691](https://doi.org/10.1051%2F0004-6361%2F201117691), [S2CID](/source/S2CID_(identifier)) [55586789](https://api.semanticscholar.org/CorpusID:55586789).

1. ^ [***a***](#cite_ref-Arcos2018_7-0) [***b***](#cite_ref-Arcos2018_7-1) [***c***](#cite_ref-Arcos2018_7-2) [***d***](#cite_ref-Arcos2018_7-3) [***e***](#cite_ref-Arcos2018_7-4) Arcos, C.; et al. (March 2018), "Stellar parameters and H α line profile variability of Be stars in the BeSOS survey", *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-belle2012_8-0) [***b***](#cite_ref-belle2012_8-1) Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", *The Astronomy and Astrophysics Review*, **20** (1): 51, [arXiv](/source/ArXiv_(identifier)):[1204.2572](https://arxiv.org/abs/1204.2572), [Bibcode](/source/Bibcode_(identifier)):[2012A&ARv..20...51V](https://ui.adsabs.harvard.edu/abs/2012A&ARv..20...51V), [doi](/source/Doi_(identifier)):[10.1007/s00159-012-0051-2](https://doi.org/10.1007%2Fs00159-012-0051-2), [S2CID](/source/S2CID_(identifier)) [119273474](https://api.semanticscholar.org/CorpusID:119273474).

1. **[^](#cite_ref-SIMBAD_9-0)** ["HD 83953"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+83953). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2018-07-25.

1. **[^](#cite_ref-Eggleton2008_10-0)** Eggleton, P. P.; Tokovinin, A. A. (2008), "A catalogue of multiplicity among bright stellar systems", *Monthly Notices of the Royal Astronomical Society*, **389** (2): 869, [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-Merrill1933_11-0)** Merrill, Paul W.; Burwell, Cora G. (September 1933), "Catalogue and Bibliography of Stars of Classes B and A whose Spectra have Bright Hydrogen Lines", *Astrophysical Journal*, **78**: 87, [Bibcode](/source/Bibcode_(identifier)):[1933ApJ....78...87M](https://ui.adsabs.harvard.edu/abs/1933ApJ....78...87M), [doi](/source/Doi_(identifier)):[10.1086/143490](https://doi.org/10.1086%2F143490).

1. **[^](#cite_ref-Arcos2017_12-0)** Arcos, C.; et al. (June 2017), "Evidence for Different Disk Mass Distributions Between Early and Late-Type Be Stars in the BeSOS Survey", *The Astrophysical Journal*, **842** (1): 18, [arXiv](/source/ArXiv_(identifier)):[1704.08133](https://arxiv.org/abs/1704.08133), [Bibcode](/source/Bibcode_(identifier)):[2017ApJ...842...48A](https://ui.adsabs.harvard.edu/abs/2017ApJ...842...48A), [doi](/source/Doi_(identifier)):[10.3847/1538-4357/aa6f5f](https://doi.org/10.3847%2F1538-4357%2Faa6f5f), [S2CID](/source/S2CID_(identifier)) [119418279](https://api.semanticscholar.org/CorpusID:119418279), 48.

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 [HD 83953](https://en.wikipedia.org/wiki/HD_83953) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/HD_83953?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.