Mu Crucis
| Observation data Epoch J2000 Equinox | |
|---|---|
| Constellation | Crux |
| μ1 Crucis | |
| Right ascension | 12h 54m 35.6249s |
| Declination | −57° 10′ 40.527″ |
| Apparent magnitude (V) | 4.03 |
| μ2 Crucis | |
| Right ascension | 12h 54m 36.8865s |
| Declination | −57° 10′ 07.214″ |
| Apparent magnitude (V) | 5.19 |
| Characteristics | |
| μ1 Cru | |
| Spectral type | B2IV-V |
| U−B color index | −0.75 |
| B−V color index | −0.17 |
| μ2 Cru | |
| Spectral type | B5Vne |
| U−B color index | −0.50 |
| B−V color index | −0.11 |
| Astrometry | |
| μ1 Cru | |
| Radial velocity (Rv) | +13.9 km/s |
| Proper motion (μ) | RA: −30.45 mas/yr Dec.: −13.55 mas/yr |
| Parallax (π) | 9.6267±0.3611 mas |
| Distance | 340 ± 10 ly (104 ± 4 pc) |
| Absolute magnitude (MV) | −1.49 |
| μ2 Cru | |
| Radial velocity (Rv) | +13 km/s |
| Proper motion (μ) | RA: −32.35 mas/yr Dec.: −10.93 mas/yr |
| Parallax (π) | 8.9486 ± 0.2264 mas |
| Distance | 364 ± 9 ly (112 ± 3 pc) |
| Absolute magnitude (MV) | −0.40 |
| Details | |
| μ1 Cru | |
| Mass | 7.7 M☉ |
| Luminosity | 1,123 L☉ |
| Surface gravity (log g) | 3.93 cgs |
| Temperature | 21,100 K |
| Metallicity [Fe/H] | −0.21 dex |
| Age | 9.2 Myr |
| μ2 Cru | |
| Mass | 5.0 M☉ |
| Radius | 3.9 R☉ |
| Luminosity | 205 L☉ |
| Surface gravity (log g) | 3.40 cgs |
| Temperature | 20,400 K |
| Rotational velocity (v sin i) | 210 km/s |
| Age | 15.9 Myr |
| Other designations | |
| μ Cru, WD 12546-5711, CCDM 12546-5711 | |
| μ1 Cru: HR 4898, CD−56°4688, HD 112092, SAO 240366, HIP 63003 | |
| μ2 Cru: HR 4899, CD−56°4689, HD 112091, SAO 240367, HIP 63005 | |
| Database references | |
| SIMBAD | μ Cru |
| μ1 Cru | |
| μ2 Cru | |
Mu Crucis, Latinized from μ Crucis, is the seventh-brightest star in the constellation Crux commonly known as the Southern Cross. μ Crucis is a wide double star of spectral class B stars, magnitude 4.0 and 5.2 respectively. They lie about 370 light-years away, and both stars are likely physically attached. The brighter component is known as μ1 Crucis or μ Crucis A, while the fainter is μ2 Crucis or μ Crucis B.
μ1 Crucis is the brighter of the two stars with an apparent magnitude of 4.0. It is a hot massive main sequence or subgiant star, over a thousand times as luminous as the sun.
μ2 Crucis is the fainter of the pair. Its apparent magnitude is 5.2 and it is a Be star, a star spinning so quickly that it has ejected a disc of material that creates emission lines in its spectrum. The disc is inclined at 36° to our line of sight.