Kappa Centauri

κ Centauri
Location of κ Centauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 14h 59m 09.68494s[1]
Declination −42° 06′ 15.1069″
Apparent magnitude (V) +3.14[2]
Characteristics
Spectral type B2 IV[3]
U−B color index −0.805[2]
B−V color index −0.204[2]
Variable type Candidate β Cep[4]
Astrometry
Radial velocity (Rv)+8.0[5] km/s
Proper motion (μ) RA: −17.62[1] mas/yr
Dec.: −22.51[1] mas/yr
Parallax (π)8.51 ± 0.54 mas[1]
Distance380 ± 20 ly
(118 ± 7 pc)
Absolute magnitude (MV)–2.2[6]
Details
κ Cen A
Mass7.2 ± 0.5[3] M☉
Radius4.4 ± 0.7[3] R☉
Luminosity2,500[3] L☉
Surface gravity (log g)4.02 ± 0.20[3] cgs
Temperature19,800 ± 900[3] K
Rotational velocity (v sin i)10[7] km/s
Age18.2 ± 3.2[8] Myr
κ Cen B
Mass5[9] M☉
Other designations
CD−41°9342,FK5 553, HD 132200, HIP 73334, HR 5576, SAO 225344.[10]
Database references
SIMBADdata

Kappa Centauri (κ Cen, κ Centauri) is a binary star in the southern constellation of Centaurus. With an apparent visual magnitude of +3.14,[2] it can be viewed with the naked eye on a dark night. Parallax measurements place it at an estimated distance of 380 light-years (120 parsecs) from Earth.[1]

This is a spectroscopic binary system where the presence of an orbiting companion is revealed by shifts in the absorption lines caused by the Doppler effect. The primary component is a huge star, with about seven times the Sun's mass and four times the Sun's radius.[3] It has a stellar classification of B2 IV,[3] indicating that it is in the subgiant stage of its stellar evolution. An effective temperature of 19,800 K[3] in the outer envelope is what gives it the blue-white hue of a B-type star.[11]

The primary is a candidate Beta Cephei variable that shows line-profile variations in its spectrum. However, the nature of the variability remains uncertain because of the binary nature of the system.[4] As of 2007, the secondary component was separated from the primary by 0.128 arcseconds at a position angle of 156°. It has about 68% of the mass of the primary.[9] This system is a proper motion member of the Upper Centaurus–Lupus sub-group in the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.[6]

In Chinese, 騎官 (Qí Guān), meaning Imperial Guards, refers to an asterism consisting of κ Centauri, γ Lupi, δ Lupi, β Lupi, λ Lupi, ε Lupi, μ Lup, π Lupi, ο Lupi and α Lupi.[12] Consequently, the Chinese name for κ Centauri itself is 騎官三 (Qí Guān sān, English: the Third Star of Imperial Guards.).[13] From this Chinese name, the name Ke Kwan has appeared.[14]

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  2. ^ a b c d Cite error: The named reference apjs15_459 was invoked but never defined (see the help page).
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  4. ^ a b Cite error: The named reference asp2002_204 was invoked but never defined (see the help page).
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  6. ^ a b Cite error: The named reference aaa216_1_44 was invoked but never defined (see the help page).
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  9. ^ a b Cite error: The named reference aaa474_1_77 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference csiro was invoked but never defined (see the help page).
  12. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  13. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 25 日
  14. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Centaurus