Beta Aurigae (Latinized from β Aurigae, abbreviated Beta Aur, β Aur), officially named Menkalinan /mɛŋˈkælɪnæn/,[10][11] is a binary star[12] system in the northern constellation of Auriga. The combined apparent visual magnitude of the system is 1.9,[4] making it the second-brightest member of the constellation after Capella. Using the parallax measurements made during the Hipparcos mission, the distance to this star system can be estimated as 81.1 light-years (24.9 parsecs), give or take a half-light-year margin of error.[1]
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Auriga |
Right ascension | 05h 59m 31.72293s[1] |
Declination | +44° 56′ 50.7573″[1] |
Apparent magnitude (V) | 1.89 - 1.98[2] |
Characteristics | |
Spectral type | A1m IV + A1m IV[3] |
U−B color index | +0.05[4] |
B−V color index | +0.03[4] |
R−I color index | –0.01 |
Variable type | Algol variable[2] |
Astrometry | |
Radial velocity (Rv) | –18.2[5] km/s |
Proper motion (μ) | RA: –56.44[1] mas/yr Dec.: –0.95[1] mas/yr |
Parallax (π) | 40.21 ± 0.23 mas[1] |
Distance | 81.1 ± 0.5 ly (24.9 ± 0.1 pc) |
Absolute magnitude (MV) | 0.55/0.76[6] |
Orbit[7] | |
Period (P) | 3.96004 days |
Eccentricity (e) | 0.0 |
Inclination (i) | 76.0 ± 0.4° |
Periastron epoch (T) | 54539.0162 ± 0.0003 reduced HJD |
Semi-amplitude (K1) (primary) | 108.053 ± 0.072 km/s |
Semi-amplitude (K2) (secondary) | 110.911 ± 0.071 km/s |
Details | |
β Aur Aa | |
Mass | 2.389 ± 0.013[7] M☉ |
Radius | 2.77[8] R☉ |
Luminosity | 55[8] L☉ |
Surface gravity (log g) | 3.93[6] cgs |
Temperature | 9,350[8] K |
Rotational velocity (v sin i) | 33[8] km/s |
Age | 570[8] Myr |
β Aur Ab | |
Mass | 2.327 ± 0.013[7] M☉ |
Radius | 2.63[8] R☉ |
Luminosity | 47[8] L☉ |
Temperature | 9,200[8] K |
Rotational velocity (v sin i) | 34[8] km/s |
Other designations | |
Database references | |
SIMBAD | data |
It is moving closer to the Sun, and in around one million years, Beta Aurigae will become the brightest star in the night sky.[13]
β Aurigae is the star system's Bayer designation. The traditional name Menkalinan is derived from the Arabic منكب ذي العنان mankib ðī-l-‘inān "shoulder of the rein-holder". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[14] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[15] included a table of the first two batches of names approved by the WGSN; which included Menkalinan for this star.
It is known as 五車三 (the Third Star of the Five Chariots) in traditional Chinese astronomy.
Beta Aurigae is a binary star system, but it appears as a single star in the night sky. The two stars are metallic-lined subgiant stars belonging to the A-type stellar classification;[3] they have roughly the same mass and radius. A-type entities are hot stars that release a blue-white hued light; these two stars burn brighter and with more heat than the Sun, which is a G2-type main sequence star. The pair constitute an eclipsing spectroscopic binary; the combined apparent magnitude varies over a period of 3.96 days between +1.89 and +1.94, as every 47.5 hours one of the stars partially eclipses the other from Earth's perspective.[16] The two stars are designated Aa and Ab in modern catalogues,[17][18] but have also been referred to as components 1 and 2 or A and B.[7][8]
There is an 11th magnitude optical companion with a separation of 187″ as of 2011, but increasing. It is also an A-class subgiant, but is an unrelated background star.[17]
At an angular separation of 13.9±0.3 arcseconds along a position angle of 155° is a companion star that is 8.5 magnitudes fainter than the primary. It may be the source of the X-ray emission from the vicinity.[19] The Beta Aurigae system is believed to be a stream member of the Ursa Major Moving Group.[20]