Beta Aurigae information

β Aurigae
	Location of β Aurigae (circled)
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Auriga
Right ascension	05h 59m 31.72293s
Declination	+44° 56′ 50.7573″
Apparent magnitude (V)	1.89 - 1.98
Characteristics
Spectral type	A1m IV + A1m IV
U−B color index	+0.05
B−V color index	+0.03
R−I color index	–0.01
Variable type	Algol variable
Astrometry
Radial velocity (Rv)	–18.2 km/s
Proper motion (μ)	RA: –56.44 mas/yr ; Dec.: –0.95 mas/yr
Parallax (π)	40.21 ± 0.23 mas
Distance	81.1 ± 0.5 ly ; (24.9 ± 0.1 pc)
Absolute magnitude (MV)	0.55/0.76
Orbit
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 M☉
Radius	2.77 R☉
Luminosity	55 L☉
Surface gravity (log g)	3.93 cgs
Temperature	9,350 K
Rotational velocity (v sin i)	33 km/s
Age	570 Myr
β Aur Ab
Mass	2.327 ± 0.013 M☉
Radius	2.63 R☉
Luminosity	47 L☉
Temperature	9,200 K
Rotational velocity (v sin i)	34 km/s
Other designations
	Menkalinan, 34 Aurigae, ADS 4556, BD+44 1328, FK5 227, HD 40183, HIP 28360, HR 2088, SAO 40750.
Database references
SIMBAD	data

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]

Along their respective orbits around the Milky Way, Beta Aurigae and the Sun are closing in on each other, so that in around one million years it will become the brightest star in the night sky.^[13]

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^ ^a ^b ^c Cite error: The named reference aj142_1_6 was invoked but never defined (see the help page).
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Cite error: The named reference Nordstrom was invoked but never defined (see the help page).
^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
^ Cite error: The named reference mnras389_2_869 was invoked but never defined (see the help page).
^ Tomkin, Jocelyn (April 1998). "Once and Future Celestial Kings". Sky and Telescope. 95 (4): 59–63. Bibcode:1998S&T....95d..59T. – based on computations from HIPPARCOS data. (The calculations exclude stars whose distance or proper motion is uncertain.) PDF^{[permanent dead link]}

[aaa474_2_653-1] ^ ^a ^b ^c ^d ^e ^f Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).

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[gcsrv-5] Cite error: The named reference gcsrv was invoked but never defined (see the help page).

[aar18_1_2-6] Cite error: The named reference aar18_1_2 was invoked but never defined (see the help page).

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[Nordstrom-8] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Cite error: The named reference Nordstrom was invoked but never defined (see the help page).

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[Kunitzsch-10] Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.

[IAU-CSN-11] "IAU Catalog of Star Names". Retrieved 28 July 2016.

[mnras389_2_869-12] Cite error: The named reference mnras389_2_869 was invoked but never defined (see the help page).

[tomkin1998-13] Tomkin, Jocelyn (April 1998). "Once and Future Celestial Kings". Sky and Telescope. 95 (4): 59–63. Bibcode:1998S&T....95d..59T. – based on computations from HIPPARCOS data. (The calculations exclude stars whose distance or proper motion is uncertain.) PDF^{[permanent dead link]}

Observation data Epoch J2000.0 Equinox J2000.0
Location of β Aurigae (circled)
Constellation	Auriga
Right ascension	05^h 59^m 31.72293^s^[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 (R_v)	–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 (M_V)	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
Menkalinan, 34 Aurigae, ADS 4556, BD+44 1328, FK5 227, HD 40183, HIP 28360, HR 2088, SAO 40750.^[9]
Database references
SIMBAD	data

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