Epsilon Centauri

ε Centauri
Location of ε Centauri (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Centaurus
Right ascension 13h 39m 53.25774s[1]
Declination −53° 27′ 59.0081″[1]
Apparent magnitude (V) +2.30[2] (2.29 - 2.31[3])
Characteristics
Spectral type B1 III[4]
U−B color index −0.92[2]
B−V color index −0.22[2]
Variable type β Cep[3]
Astrometry
Radial velocity (Rv)+3.0[5] km/s
Proper motion (μ) RA: −15.30[1] mas/yr
Dec.: −11.72[1] mas/yr
Parallax (π)7.63 ± 0.48 mas[1]
Distance430 ± 30 ly
(131 ± 8 pc)
Absolute magnitude (MV)–3.9[6]
Details
Mass11.60 ± 1.06[4] M☉
Luminosity15,217[4] L☉
Surface gravity (log g)3.68[6] cgs
Temperature24,000[4] K
Metallicity [Fe/H]–0.14 ± 0.10[7] dex
Rotational velocity (v sin i)160[8] km/s
Age15.8 ± 5.7[9] Myr
Other designations
CP−52 6655, FK5 504, HD 118716, HIP 66657, HR 5132, SAO 241047.
Database references
SIMBADdata

Epsilon Centauri (ε Cen, ε Centauri) is a star in the southern constellation of Centaurus. It is one of the brightest stars in the constellation with a slightly variable apparent visual magnitude of +2.30. Parallax measurements put it at a distance of around 430 light-years (130 parsecs) from Earth.

In Chinese, 南門 (Nán Mén), meaning Southern Gate, refers to an asterism consisting of ε Centauri and α Centauri.[10] Consequently, the Chinese name for ε Centauri itself is 南門一 (Nán Mén yī, English: the First Star of Southern Gate.)[11]

A yellow-light light curve for Epsilon Centauri, adapted from Shobbrook (1972)[12]

ε Centauri is a massive star with nearly 12 times the mass of the Sun.[4] The spectrum matches a stellar classification of B1 III,[4] indicating this is an evolved giant star. It is radiating more than 15,000[4] times the luminosity of the Sun from its outer atmosphere at an effective temperature of 24,000 K,[4] giving it the blue-white hue of a B-type star.[13] This is classified as a Beta Cephei type variable star with a primary period of 0.16961 days (4 hours 4 minutes), completing 5.9 cycles per day.[7] During each cycle, the brightness of the star varies from apparent magnitude +2.29 to +2.31.

This star is a proper motion member of the Lower Centaurus–Crux sub-group in the Scorpius–Centaurus OB association, the nearest such association of co-moving massive stars to the Sun.[6] Epsilon Centauri is a relatively young star, with an age of around 16 million years.[9]

The IAU has not assigned a proper name to this star.[14]

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