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Eta Centauri

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Eta Centauri

Eta Centauri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 14h 35m 30.42416s[1]
Declination −42° 09′ 28.1708″[1]
Apparent magnitude (V) +2.35[2] (2.30 - 2.41[3])
Characteristics
Spectral type B1.5 Vne[4]
U−B color index −0.862[2]
B−V color index −0.215[2]
Variable type γ Cassiopeiae[3]
Astrometry
Radial velocity (Rv) –0.2[5] km/s
Proper motion (μ) RA: −34.73[1] mas/yr
Dec.: −32.72[1] mas/yr
Parallax (π) 10.67 ± 0.21[1] mas
Distance 306 ± 6 ly
(94 ± 2 pc)
Details
Mass 12.0 ± 0.3[6] M
Radius 5-6 R
Luminosity 8,700[4] L
Surface gravity (log g) 3.20[7] cgs
Temperature 25,700[4] K
Rotational velocity (v sin i) 330[4] km/s
Age 5.6 ± 1.0[6] Myr
Other designations
CD−41°8917, CP−41°6839, FK5 537, HD 127972, HIP 71352, HR 5440, SAO 225044.[8]
Database references
SIMBAD data

Eta Centauri (η Cen, η Centauri) is a star in the southern constellation of Centaurus. It has an apparent visual magnitude of +2.35[2] and is located at a distance of around 306 light-years (94 parsecs).[1] In traditional Chinese astronomy, Eta Centauri was known as 庫樓二[9] (meaning: the Second (Star) of Koo Low).[10]

The stellar classification of this star is B1.5 Vne,[4] indicating that it is a B-type main sequence star. The 'n' suffix means that the absorption lines are broadened from rapid rotation. It has a projected rotational velocity of 330 km s−1[4] and completes a full rotation in less than a day. This is a Be star as shown by the 'e' suffix,[11] which means it has variable emissions in its hydrogen spectral lines. This emission can be modeled by a decretion disk of gas that has been ejected from the star and now follows a near Keplerian orbit around the central body.[12] Finally it is slightly variable, and classified as a Gamma Cassiopeiae variable star with multiple periods of variability.[3]

Eta Centauri has about 12[6] times the mass of the Sun, placing it above the dividing line between stars that evolve into white dwarfs and those that turn into supernovae. It is radiating 8,700[4] times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 25,700 K.[4] This heat causes the star to glow with the blue-white hue common to B-type stars.[13] Eta Centauri 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.[7]

See also

References

  1. ^ a b c d e f
  2. ^ a b c d
  3. ^ a b c
  4. ^ a b c d e f g h
  5. ^
  6. ^ a b c
  7. ^ a b
  8. ^
  9. ^ (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.
  10. ^
  11. ^
  12. ^
  13. ^

External links

  • Eta Centauri by Jim Kaler.
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