Mu Crucis

Mu Crucis
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]
Distance340 ± 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]
Distance364 ± 9 ly
(112 ± 3 pc)
Absolute magnitude (MV)−0.40[7]
Details
μ1 Cru
Mass7.7[9] M☉
Luminosity1,123[7] L☉
Surface gravity (log g)3.93[10] cgs
Temperature21,100[10] K
Metallicity [Fe/H]−0.21[7] dex
Age9.2[9] Myr
μ2 Cru
Mass5.0[9] M☉
Radius3.9[11] R☉
Luminosity205[7] L☉
Surface gravity (log g)3.40[12] cgs
Temperature20,400[11] K
Rotational velocity (v sin i)210[12] km/s
Age15.9[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
SIMBADμ 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.[11]

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