# Delta Centauri

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Star in the constellation Centaurus

δ Centauri Location of δ Centauri (circled) Observation data Epoch J2000 Equinox J2000 Constellation Centaurus[1] Right ascension 12h 08m 21.49764s[2] Declination −50° 43′ 20.7386″[2] Apparent magnitude (V) +2.57[3] (2.51 - 2.65[4]) Characteristics Spectral type B2Vne[5] or B2 IVne[6] U−B color index −0.92[3] B−V color index −0.13[3] Variable type γ Cas[4] Astrometry Radial velocity (Rv) +11[7] km/s Proper motion (μ) RA: −49.94< mas/yr[2] Dec.: −7.19 mas/yr[2] Parallax (π) 7.86±0.47 mas[2] Distance 410 ± 20 ly (127 ± 8 pc) Absolute magnitude (MV) −2.94[1] Details Mass 8.7±0.3[5] M☉ Radius 8.18±0.16[8] R☉ Luminosity 5,129[5] L☉ Surface gravity (log g) 3.43±0.03[8] cgs Temperature 22,230±650[5] K Rotational velocity (v sin i) 263±14[9] km/s Age 21.5±1.5[10] Myr Other designations δ Cen, CD−50°6697, CPD−50°4862, FK5 452, HD 105435, HIP 59196, HR 4621, SAO 239689[11] Database references SIMBAD data

**Delta Centauri** is a [star](/source/Star) in the southern [constellation](/source/Constellation) of [Centaurus](/source/Centaurus). Its name is a [Bayer designation](/source/Bayer_designation) that is [Latinized](/source/Romanization_of_Greek) from δ Centauri, and abbreviated Delta Cen or δ Cen. The [apparent visual magnitude](/source/Apparent_visual_magnitude) of this star is +2.57,[3] making it readily visible to the [naked eye](/source/Naked_eye). Based upon [parallax](/source/Stellar_parallax) measurements, it is located at a distance of about 410 [light-years](/source/Light-year) (130 [parsecs](/source/Parsec)) from the [Earth](/source/Earth).[2] The star is drifting further away with a [radial velocity](/source/Radial_velocity) of +11 km/s.[7]

## Properties

A [light curve](/source/Light_curve) for Delta Centauri, plotted from *[Hipparcos](/source/Hipparcos)* data[12]

δ Centauri is a [shell star](/source/Shell_star), with a distinctive [spectrum](/source/Stellar_spectrum) created by material thrown off into a disk by its rapid rotation. It is also a [variable star](/source/Variable_star) whose brightness varies from magnitude +2.51 to +2.65. It has been classified as a [γ Cassiopeiae type](/source/Gamma_Cassiopeiae_variable) variable.[13] The energy from this star is being radiated at an [effective temperature](/source/Effective_temperature) of over 22,000 K from the outer envelope, giving it the blue-white hue of a [B-type star](/source/B-type_star).[14] It has a radius of 6.5 times the [radius of the Sun](/source/Solar_radius)[15] and 8.7 times the [Sun's mass](/source/Solar_mass).[15]

The [stellar classification](/source/Stellar_classification) of this star is B2Vne,[5] which presents as a [B-type main-sequence star](/source/B-type_main-sequence_star). [N. Houk](/source/Nancy_Houk) in 1979 found a class of B2IVne,[6] with the [luminosity class](/source/Luminosity_class) of IV suggesting that this may be a [subgiant star](/source/Subgiant_star) that has exhausted the hydrogen at its core and begun to [evolve](/source/Stellar_evolution) away from the [main sequence](/source/Main_sequence). Detailed study of the spectrum suggests that the disparity is due to [gravity darkening](/source/Gravity_darkening) which makes the subgiant spectrum appear similar to a main-sequence star.[16] The star is spinning rapidly, with the resulting [Doppler effect](/source/Doppler_effect) giving its spectrum broad [absorption lines](/source/Absorption_line) as indicated by the 'n'. The suffix 'e' means this is a classical [Be star](/source/Be_star), which is a type of hot star that has not yet evolved into a [supergiant](/source/Supergiant_star) and is surrounded by circumstellar gas. The presence of this gas creates an [excess emission of infrared](/source/Infrared_excess), along with [emission lines](/source/Emission_line) in the star's spectrum. Most of it is concentrated around the equator, forming a disk.[15]

Some of the variation in this star may be explained by assuming it is a [binary star](/source/Binary_star) system. This proposed secondary star would need to have about 4–7 times the Sun's mass and be orbiting with a period of at least 4.6 years at a minimum separation of 6.9 [Astronomical Units](/source/Astronomical_Unit).[13] δ Centauri shares a [common proper motion](/source/Common_proper_motion) with the nearby stars [HD 105382](/source/HD_105382) and HD 105383, so they may form a small cluster or perhaps a triple star system.[13] It is a [proper motion](/source/Proper_motion) member of the Lower Centaurus–Crux sub-group in the [Scorpius–Centaurus](/source/Scorpius%E2%80%93Centaurus_association) [OB association](/source/Stellar_association), the nearest such of association of co-moving massive stars to the Sun.[17]

## Etymology

In [Chinese](/source/Chinese_language), 馬尾 (*Mǎ Wěi*), meaning *[Horse's Tail](/source/Chinese_constellations#The_Southern_Asterisms_(近南極星區))*, refers to an asterism consisting of δ Centauri, [G Centauri](/source/G_Centauri) and [ρ Centauri](/source/Rho_Centauri).[18] Consequently, δ Centauri itself is known as 馬尾三 (*Mǎ Wěi sān*, English: the Third Star of Horse's Tail.).[19] From this Chinese name, the name **Ma Wei** appeared.[20]

The people of [Aranda](/source/Aranda_people) and [Luritja](/source/Luritja) tribe around [Hermannsburg](/source/Hermannsburg), [Central Australia](/source/Central_Australia), named **Iritjinga**, "The Eagle-hawk", a quadrangular arrangement comprising this star, [γ Cen](/source/Gamma_Centauri) (Muhlifain), [γ Cru](/source/Gamma_Crucis) (Gacrux), and [δ Cru](/source/Delta_Crucis) (Imai).[21]

## See also

- [Traditional Chinese star names](/source/Traditional_Chinese_star_names#Centaurus)

## References

1. ^ [***a***](#cite_ref-Anderson2012_1-0) [***b***](#cite_ref-Anderson2012_1-1) 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=59196&-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).

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1. ^ [***a***](#cite_ref-aaa488_3_L67_13-0) [***b***](#cite_ref-aaa488_3_L67_13-1) [***c***](#cite_ref-aaa488_3_L67_13-2) Meilland, A.; et al. (September 2008), ["δ Centauri: a new binary Be star detected by VLTI/AMBER spectro-interferometry"](https://hal.archives-ouvertes.fr/hal-00307590), *Astronomy and Astrophysics*, **488** (3): L67–L70, [arXiv](/source/ArXiv_(identifier)):[0807.4622](https://arxiv.org/abs/0807.4622), [Bibcode](/source/Bibcode_(identifier)):[2008A&A...488L..67M](https://ui.adsabs.harvard.edu/abs/2008A&A...488L..67M), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:200810624](https://doi.org/10.1051%2F0004-6361%3A200810624), [S2CID](/source/S2CID_(identifier)) [118737029](https://api.semanticscholar.org/CorpusID:118737029)

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v t e Constellation of Centaurus List of stars in Centaurus Centaurus in Chinese astronomy Stars Bayer α A (Rigil Kentaurus) B (Toliman) C (Proxima Centauri) β (Hadar) γ δ ε ζ (Leepwal) η θ (Menkent) ι (Kulou) κ λ μ ν (Heng) ξ1 ξ2 ο1 ο2 π ρ σ τ υ1 υ2 φ χ ψ x1 x2 C3 D E F G H J K M N Q Flamsteed 1 (i) 2 (g) 3 (k) 4 (h) Variable R T V Y RR SV SX BV DY UY V346 V553 V744 V752 V761 (a) V763 (C1) V766 V779 (Krzemiński's star) V803 V810 V816 (Przybylski's Star) V831 V842 V885 V886 V863 V1032 V1369 V1400 V1935 HR 4460 (A) 4466 (C2) 4499 4522 4523 4537 (j) 4546 (B) 4721 4748 (u) 4796 4817 (l) 4831 (w) 4874 (p) 4888 (e) 4889 (n) 4940 (f) 4979 4989 5006 (r) 5041 (m) 5089 (d) 5174 (z) 5222 (y) 5224 5241 5297 5358 (v) 5371 5471 (b) 5485 (c1) 5489 (c2) HD 97413 98176 100453 101581 101930 102117 (Uklun) 103197 107914 108236 109749 110113 113538 113766 114386 114729 115600 116434 (Matza) 117207 117618 (Dofida) 117939 120411 121228 121504 124448 (Popper's Star) 125072 125595 131399 Other 2MASS J1126−5003 2M1207 Gaia BH2 HD 131399 Ab PSR B1259−63 PSR J1311−3430 TOI-763 WASP-15 (Nyamien) WASP-41 WASP-42 WASP-167/KELT-13 Exoplanets 2M1207b b Centauri b HD 101930 b HD 102117 b (Leklsullun) HD 103197 b HD 109749 b HD 113538 b c HD 114386 b HD 114729 b HD 117207 b HD 117618 b (Noifasui) HD 121504 b HIP 65426 b (Najsakopajk) HIP 67522 b NGTS-13b Proxima Centauri b c d WASP-15b (Asye) Star clusters NGC 3766 4230 4507 5281 5286 5316 5460 5617 5662 Other IC 2944 ω Centauri Scorpius–Centaurus association Stock 16 Nebulae NGC 3918 5307 Other Boomerang Nebula Fleming 1 G292.0+1.8 G306.3-0.9 Gum 41 IC 2944 IRAS 13208−6020 RCW 79 RCW 86 Southern Crab Nebula SuWt 2 Galaxies NGC 3557 3568 3749 3783 4444 4603 4622 4650A 4683 4696 4706 4709 4729 4730 4743 4744 4909 4930 4945 4976 5011 A 5026 5064 5082 5090 5091 5102 5114 5121 5128 (Centaurus A) 5161 5206 5253 5266 5291 5398 5408 5419 5483 5516 Other ESO 269-57 ESO 325-4 ESO 383-76 ESO 444-46 Fourcade-Figueroa Object IC 3370 IC 4214 IC 4329A IRAS 13224−3809 J1144−4308 LEDA 677373 PKS 1144−379 PKS 1353−341 PKS 1424−418 Galaxy clusters Abell S740 Centaurus Cluster Shapley Supercluster Astronomical events GW190521 SN 185 SN 1895B (Z) SN 1972E SN 1986G J1407b SN 2019so Category

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