Mu Orionis
μ Orionis (Latinised to Mu Orionis, abbreviated to μ Ori or Mu Ori) is a quadruple star system 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.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Orion |
| μ Ori A | |
| Right ascension | 06h 02m 22.997s |
| Declination | +09° 38′ 50.24″ |
| Apparent magnitude (V) | 4.30 |
| μ Ori B | |
| Right ascension | 06h 02m 23.009s |
| Declination | +09° 38′ 50.52″ |
| Apparent magnitude (V) | 6.27 |
| Characteristics | |
| μ Ori A | |
| Spectral type | A1 Vm |
| U−B color index | +0.11 |
| B−V color index | +0.14 |
| μ Ori B | |
| Spectral type | F2 V |
| U−B color index | +0.00 |
| B−V color index | +0.43 |
| Astrometry | |
| Radial velocity (Rv) | 0.00 km/s |
| Proper motion (μ) | RA: 10.43 mas/yr Dec.: −39.09 mas/yr |
| Parallax (π) | 21.69 ± 0.13 mas |
| Distance | 150.4 ± 0.9 ly (46.1 ± 0.3 pc) |
| Absolute magnitude (MV) | Aa: 0.93 Ba: 3.53 Bb: 3.53 |
| Orbit | |
| 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 | |
| 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 | |
| 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 | |
| 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 km/s |
| Age | 282 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 | |
| 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 falls just outside an unrelated planetary nebula Abell 12. The bright star makes detecting the faint nebula difficult and it has been nicknamed The Hidden.