Mu Crucis
Star in the constellation Crux
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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.
 | |
| Observation data Epoch J2000 Equinox | |
|---|---|
| Constellation | Crux |
| μ1 Crucis | |
| Right ascension | 12h 54m 35.6249s[1] |
| Declination | −57° 10′ 40.527″[1] |
| Apparent magnitude (V) | 4.03[2] |
| μ2 Crucis | |
| Right ascension | 12h 54m 36.8865s[1] |
| Declination | −57° 10′ 07.214″[1] |
| Apparent magnitude (V) | 5.19[2] |
| Characteristics | |
| μ1 Cru | |
| Spectral type | B2IV-V[3] |
| U−B color index | −0.75[2] |
| B−V color index | −0.17[2] |
| μ2 Cru | |
| Spectral type | B5Vne[4] |
| U−B color index | −0.50[2] |
| B−V color index | −0.11[2] |
| Astrometry | |
| μ1 Cru | |
| Radial velocity (Rv) | +13.9[5] km/s |
| Proper motion (μ) | RA: −30.45[1] mas/yr Dec.: −13.55[1] mas/yr |
| Parallax (π) | 9.6267±0.3611 mas[6] |
| Distance | 340 ± 10 ly (104 ± 4 pc) |
| Absolute magnitude (MV) | −1.49[7] |
| μ2 Cru | |
| Radial velocity (Rv) | +13[5] km/s |
| Proper motion (μ) | RA: −32.35[1] mas/yr Dec.: −10.93[1] mas/yr |
| Parallax (π) | 8.9486±0.2264 mas[8] |
| Distance | 364 ± 9 ly (112 ± 3 pc) |
| Absolute magnitude (MV) | −0.40[7] |
| Details | |
| μ1 Cru | |
| Mass | 7.7[9] M☉ |
| Luminosity | 1,123[7] L☉ |
| Surface gravity (log g) | 3.93[10] cgs |
| Temperature | 21,100[10] K |
| Metallicity [Fe/H] | −0.21[7] dex |
| Age | 9.2[9] Myr |
| μ2 Cru | |
| Mass | 5.0[9] M☉ |
| Radius | 3.9[11] R☉ |
| Luminosity | 205[7] L☉ |
| Surface gravity (log g) | 3.40[12] cgs |
| Temperature | 20,400[11] K |
| Rotational velocity (v sin i) | 210[12] km/s |
| Age | 15.9[9] Myr |
| Other designations | |
| μ Cru, WD 12546-5711, CCDM 12546-5711[13][14] | |
| 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 | |
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.[11]