Epsilon Pegasi

Epsilon Pegasi

The position of Epsilon Pegasi in the Pegasus constellation.
Observation data Epoch J2000      Equinox J2000
Constellation	Pegasus
Right ascension	21h 44m 11.158s
Declination	+09° 52′ 30.04″
Apparent magnitude (V)	2.404
Characteristics
Spectral type	K2 Ib
U−B color index	1.7
B−V color index	1.52
Variable type	LC
Astrometry
Radial velocity (Rv)	3.39 ±0.06 km/s
Proper motion (μ)	RA: 30.02 ±1.13 mas/yr Dec.: 1.38 ±0.47 mas/yr
Parallax (π)	4.85 ± 0.84 mas
Distance	approx. 700 ly (approx. 210 pc)
Absolute magnitude (MV)	-4.19
Details
Mass	10-11 M☉
Radius	150 R☉
Luminosity	6,700 L☉
Temperature	4,460 K
Rotation	<17 km/s.
Other designations
Enif, Enf, Enir, Al Anf, Os Pegasi, Fom, 8 Peg, HR 8308, BD +09°4891, HD 206778, SAO 127029, FK5 815, HIP 107315.
Database references
SIMBAD	data

Epsilon Pegasi (ε Peg, ε Pegasi) is the brightest star in the constellation Pegasus. It has the traditional name Enif. The name "Enif" is derived from the Arabic word for nose, due to its position as the muzzle of Pegasus.

In Chinese, 危宿 (Wēi Sù), meaning Rooftop (asterism), refers to an asterism consisting of ε Pegasi, α Aquarii and θ Peg. Consequently, ε Pegasi itself is known as 危宿三 (Wēi Sù sān, English: the Third Star of Rooftop.)

It is fairly average for an orange supergiant star, well into the later stages of its stellar evolution and as such may be considered a dying star. Enif probably only has a few million years left to go, although it is unknown whether it will explode in a supernova or die off as a rare neon-oxygen white dwarf, due to its mass straddling the dividing line between stars destined to explode or not. Enif has been observed to brighten radically upon a few occasions, giving rise to the theory that it (and possibly other supergiants) erupt in massive flares that dwarf those of our own Sun. It is a type LC slow irregular variable star that varies from +0.7 to +3.5 in magnitude.

See also

• Epsilon Pegasi in fiction