Rigel

Rigel

Location of Rigel (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Orion
Pronunciation	/ˈraɪdʒəl/[1] or /-ɡəl/[2]
A
Right ascension	05h 14m 32.27210s[3]
Declination	−08° 12′ 05.8981″[3]
Apparent magnitude (V)	0.13[4] (0.05–0.18[5])
BC
Right ascension	05h 14m 32.049s[6]
Declination	−08° 12′ 14.78″[6]
Apparent magnitude (V)	6.67[7] (7.5/7.6[8])
Characteristics
A
Evolutionary stage	Blue supergiant
Spectral type	B8 Ia[9]
U−B color index	−0.66[10]
B−V color index	−0.03[10]
Variable type	Alpha Cygni[11]
BC
Evolutionary stage	Main sequence
Spectral type	B9V + B9V[12]
Astrometry
Radial velocity (Rv)	17.8±0.4[13] km/s
Proper motion (μ)	RA: +1.31[3] mas/yr Dec.: +0.50[3] mas/yr
Parallax (π)	3.2352 ± 0.0553 mas[14]
Distance	863[15][16] ly (264 pc)
Absolute magnitude (MV)	−7.84[9]
Orbit[12]
Primary	A
Companion	BC
Period (P)	24,000 yr
Orbit[7]
Primary	Ba
Companion	Bb
Period (P)	9.860 days
Eccentricity (e)	0.1
Semi-amplitude (K1) (primary)	25.0 km/s
Semi-amplitude (K2) (secondary)	32.6 km/s
Orbit[12]
Primary	B
Companion	C
Period (P)	63 yr
Details
A
Mass	21±3[17] M☉
Radius	74.1+6.1 −7.3[18] R☉
Luminosity (bolometric)	120,000+25,000 −21,000[19] L☉
Surface gravity (log g)	1.75±0.10[20] cgs
Temperature	12,100±150[20] K
Metallicity [Fe/H]	−0.06±0.10[9] dex
Rotational velocity (v sin i)	25±3[20] km/s
Age	8±1[9] Myr
Ba
Mass	3.84[12] M☉
Bb
Mass	2.94[12] M☉
C
Mass	3.84[12] M☉
Other designations
β Orionis, ADS 3823, STF 668, BU 555,[8] H II 33,[21] CCDM J05145-0812, WDS J05145-0812[22]
A: Rigel, Algebar, Elgebar, 19 Orionis, HD 34085, HR 1713, HIP 24436, SAO 131907, BD−08°1063, FK5 194
B: Rigel B, GCRV 3111
Database references
SIMBAD	Rigel
	Rigel B

Rigel is a blue supergiant star in the constellation of Orion. It has the Bayer designation β Orionis, which is Latinized to Beta Orionis and abbreviated Beta Ori or β Ori. Rigel is the brightest and most massive component – and the eponym – of a star system of at least four stars that appear as a single blue-white point of light to the naked eye. This system is located at a distance of approximately 860 light-years (260 pc) from the Sun.

A star of spectral type B8Ia, Rigel is calculated to be anywhere from 61,500 to 363,000 times as luminous as the Sun, and 18 to 24 times as massive, depending on the method and assumptions used. Its radius is more than seventy times that of the Sun, and its surface temperature is 12,100 K. Due to its stellar wind, Rigel's mass-loss is estimated to be ten million times that of the Sun. With an estimated age of seven to nine million years, Rigel has exhausted its core hydrogen fuel, expanded, and cooled to become a supergiant. It is expected to end its life as a type II supernova, leaving a neutron star or a black hole as a final remnant, depending on the initial mass of the star.

Rigel varies slightly in brightness, its apparent magnitude ranging from 0.05 to 0.18. It is classified as an Alpha Cygni variable due to the amplitude and periodicity of its brightness variation, as well as its spectral type. Its intrinsic variability is caused by pulsations in its unstable atmosphere. Rigel is generally the seventh-brightest star in the night sky and the brightest star in Orion, though it is occasionally outshone by Betelgeuse, which varies over a larger range.

A triple-star system is separated from Rigel by an angle of 9.5 arc seconds. It has an apparent magnitude of 6.7, making it 1/400th as bright as Rigel. Two stars in the system can be seen by large telescopes, and the brighter of the two is a spectroscopic binary. These three stars are all blue-white main-sequence stars, each three to four times as massive as the Sun. Rigel and the triple system orbit a common center of gravity with a period estimated to be 24,000 years. The inner stars of the triple system orbit each other every 10 days, and the outer star orbits the inner pair every 63 years. A much fainter star, separated from Rigel and the others by nearly an arc minute, may be part of the same star system.