Mu Orionis

μ Orionis (Latinised to Mu Orionis, abbreviated to μ Ori or Mu Ori) is a quadruple star system^[6] in the constellation Orion, similar to Mizar and Epsilon Lyrae with combined visual magnitude of 4.13. The four stars are known as Mu Orionis Aa, Mu Orionis Ab, Mu Orionis Ba, and Mu Orionis Bb. The A and B systems are several tenths of an arcsecond apart. The entire system is located approximately 150 light years from the Sun.

μ Orionis

Location of μ Ori (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Orion
μ Ori A
Right ascension	06h 02m 22.997s[1]
Declination	+09° 38′ 50.24″[1]
Apparent magnitude (V)	4.30[2]
μ Ori B
Right ascension	06h 02m 23.009s[1]
Declination	+09° 38′ 50.52″[1]
Apparent magnitude (V)	6.27[2]
Characteristics
μ Ori A
Spectral type	A1 Vm
U−B color index	+0.11[3]
B−V color index	+0.14[3]
μ Ori B
Spectral type	F2 V
U−B color index	+0.00[3]
B−V color index	+0.43[3]
Astrometry
Radial velocity (Rv)	0.00[4] km/s
Proper motion (μ)	RA: 10.43[5] mas/yr Dec.: −39.09[5] mas/yr
Parallax (π)	21.69±0.13 mas[6]
Distance	150.4 ± 0.9 ly (46.1 ± 0.3 pc)
Absolute magnitude (MV)	Aa: 0.93 Ba: 3.53 Bb: 3.53[3]
Orbit[6]
Primary	μ Ori A
Companion	μ Ori B
Period (P)	6,813.8±1.2 d
Semi-major axis (a)	0.2737±0.0021" (12.620±0.057 AU)
Eccentricity (e)	0.7410±0.0011
Inclination (i)	96.028±0.028°
Orbit[6]
Primary	μ Ori Aa
Companion	μ Ori Ab
Period (P)	4.4475849 days
Semi-major axis (a)	0.001661±0.000013" (0.07659±0.00058 AU)
Eccentricity (e)	0.0037±0.0014
Inclination (i)	47.1±9.0°
Semi-amplitude (K1) (primary)	1.03±0.26 km/s
Semi-amplitude (K2) (secondary)	> 4.58 km/s
Orbit[6]
Primary	μ Ori Ba
Companion	μ Ori Bb
Period (P)	4.7835349 days
Semi-major axis (a)	0.001688±0.000013" (0.07659±0.00036 AU)
Eccentricity (e)	0.0016±0.0014
Inclination (i)	110.71±0.73°
Semi-amplitude (K1) (primary)	1.72±0.26 km/s
Semi-amplitude (K2) (secondary)	2.02±0.26 km/s
Details[3][6]
μ Ori Aa
Mass	2.38 M☉
Radius	2.85 R☉
Luminosity	32.2 L☉
Temperature	8,300 K
Rotational velocity (v sin i)	10[7] km/s
Age	282[8] Myr
μ Ori Ab
Mass	0.652 M☉
μ Ori Ba
Mass	1.389 M☉
Radius	1.33 R☉
Luminosity	3.0 L☉
Temperature	6,600 K
μ Ori Bb
Mass	1.356 M☉
Radius	1.33 R☉
Luminosity	3.0 L☉
Temperature	6,600 K
Other designations
Mu Orionis, Mu Ori, μ Orionis, μ Ori, 61 Orionis, 61 Ori, HR 2124, HD 40932, HIP 28614, BD+09°1064, ADS 4617, WDS J06024+0939, 2MASS J05351889-0516140
Database references
SIMBAD	data
	data2
	data3

Mu Orionis Aa is an A5V dwarf and metallic line star, of effective temperature 8,350 Kelvin, and apparent magnitude of +4.31. Mu Orionis Aa has 2.1 solar masses, and a radius of 2.9 R_☉ and a luminosity 32 times that of the Sun.

Mu Orionis Ab is a G5V dwarf orbiting Aa at a distance of 0.077 AU, 0.2x the orbit of Mercury.

Mu Orionis Ba and Bb are F5V dwarfs with 1.4 solar masses and apparent magnitudes of 6.91. They are separated from each other by 0.078 AU.

μ Orionis is very close in the sky to the faint planetary nebula Abell 12. The star's relative brightness makes detecting the nebula difficult and it has been nicknamed The Hidden Nebula as a result.^{[citation needed]}