Epsilon Centauri

This article is about ε Centauri and is not to be confused with E Centauri or e Centauri.

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.

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]
Distance	430 ± 30 ly (131 ± 8 pc)
Absolute magnitude (MV)	–3.9[6]
Details
Mass	11.60 ± 1.06[4] M☉
Luminosity	15,217[4] L☉
Surface gravity (log g)	3.68[6] cgs
Temperature	24,000[4] K
Metallicity [Fe/H]	–0.14 ± 0.10[7] dex
Rotational velocity (v sin i)	160[8] km/s
Age	15.8 ± 5.7[9] Myr
Other designations
CP−52 6655, FK5 504, HD 118716, HIP 66657, HR 5132, SAO 241047.
Database references
SIMBAD	data

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]