Mu Crucis

Mu Crucis
Location of μ Crucis (circled in red)
Observation data
Epoch J2000      Equinox ICRS
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
Evolutionary stage subgiant
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
Distance370+23
−20 ly
(113+7
−6 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
Distance364 ± 9 ly
(112 ± 3 pc)
Absolute magnitude (MV)−0.40
Details
μ1 Cru
Mass7.0±0.1 M☉
Radius3.3±0.2 R☉
Luminosity1,740+170
−150 L☉
Surface gravity (log g)4.25±0.05 cgs
Temperature20,500±250 K
Metallicity [Fe/H]−0.21 dex
Rotational velocity (v sin i)31.3±0.2 km/s
Age9.5+5.6
−5.3 Myr
μ2 Cru
Mass5.0 M☉
Radius3.9 R☉
Luminosity205 L☉
Surface gravity (log g)3.40 cgs
Temperature20,400 K
Rotational velocity (v sin i)210 km/s
Age15.9 Myr
Other designations
μ Cru, CCDM 12546-5711, WD 12546-5711
μ1 Cru: CD−56°4688, HD 112092, HIP 63003, HR 4898, SAO 240366
μ2 Cru: CD−56°4689, HD 112091, HIP 63005, HR 4899, SAO 240367
Database references
SIMBADμ Cru
μ1 Cru
μ2 Cru

Mu Crucis is a double star in the southern constellation of Crux, which is commonly known as the Southern Cross. Its name is a Bayer designation that is Latinized from μ Crucis and abbreviated Mu Cru or μ Cru. μ Crucis is a wide pair of spectral class B stars, magnitude 4.0 and 5.2 respectively, forming the seventh-brightest star in the constellation. 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.

References

  1. 1 2 3 4 5 6 7 8 Perryman, M. A. C.; et al. (April 1997). "The HIPPARCOS Catalogue". Astronomy & Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P.
  2. 1 2 3 4 5 6 Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
  3. 1 2 3 4 5 6 7 8 9 10 Aschenbrenner, P.; Przybilla, N. (2026-04-03). "Quantitative spectroscopy of single and multiple OB-type stars. Non-LTE spectrum analysis with machine learning". Astronomy and Astrophysics. arXiv:2604.03082.
  4. ↑ Hiltner, W. A.; et al. (1969). "MK Spectral Types for Bright Southern OB Stars". The Astrophysical Journal. 157: 313. Bibcode:1969ApJ...157..313H. doi:10.1086/150069.
  5. ↑ Levenhagen, R. S.; Leister, N. V. (2006). "Spectroscopic analysis of southern B and be stars". Monthly Notices of the Royal Astronomical Society. 371 (1): 252–262. arXiv:astro-ph/0606149. Bibcode:2006MNRAS.371..252L. doi:10.1111/j.1365-2966.2006.10655.x. S2CID 16492030.
  6. 1 2 Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Bibcode:1967IAUS...30...57E.
  7. ↑ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  8. 1 2 3 4 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  9. ↑ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  10. 1 2 Tetzlaff, N.; et al. (2011). "A catalogue of young runaway Hipparcos stars within 3 KPC from the Sun". Monthly Notices of the Royal Astronomical Society. 410 (1): 190. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873.
  11. 1 2 3 Zorec, J.; et al. (2007). "Be star disc characteristics near the central object". Astronomy & Astrophysics. 470 (1): 239–247. Bibcode:2007A&A...470..239Z. doi:10.1051/0004-6361:20066615. hdl:11336/38181.
  12. 1 2 Chauville, J.; et al. (2001). "High and intermediate-resolution spectroscopy of be stars 4481 lines" (PDF). Astronomy and Astrophysics. 378: 861. Bibcode:2001A&A...378..861C. doi:10.1051/0004-6361:20011202. Retrieved 2026-09-12.
  13. ↑ "HR 4898". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-06-08.
  14. ↑ "HIP 63005". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-06-08.