Mu Columbae

Mu Columbae (μ Col, μ Columbae) is a star in the constellation of Columba. It is one of the few O-class stars that are visible to the unaided eye.^[8] The star is known to lie approximately 1,900 light years from the Solar System (with an error margin of a few hundred light years).^[6]

μ Columbae

Location of μ Columbae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Columba
Right ascension	05h 45m 59.89502s[1]
Declination	−32° 18′ 23.1623″[1]
Apparent magnitude (V)	5.18[2]
Characteristics
Spectral type	O9.5 V[3]
U−B color index	−1.06[2]
B−V color index	−0.28[2]
Variable type	Suspected[4]
Astrometry
Radial velocity (Rv)	+109.00 ± 1.8[5] km/s
Proper motion (μ)	RA: +3.271 mas/yr[1] Dec.: −22.176 mas/yr[1]
Parallax (π)	1.7024 ± 0.0898 mas[1]
Distance	1,894±111 ly (581±34 pc)[6]
Absolute magnitude (MV)	−3.78±0.11[6]
Details[6]
Mass	18.9±0.3 M☉
Radius	6.3±0.4 R☉
Luminosity	43,650+4,210 −3,840 L☉
Surface gravity (log g)	4.12±0.05 cgs
Temperature	33,400±300 K
Rotational velocity (v sin i)	125±8 km/s
Age	2 – 4[7] Myr
Other designations
HR 1996, CD−32°2538, HD 38666, SAO 196149, HIP 27204
Database references
SIMBAD	data

This is a relatively fast rotating star that completes a full revolution approximately every 1.5 days. (Compare this to the Sun, which at only 22 percent of this star's diameter rotates only once every 25.4 days.) This rate of rotation is fairly typical for stars of this class.

Based on measurements of proper motion and radial velocity, astronomers know that this star and AE Aurigae are moving away from each other at a relative velocity of over 200 km/s. Their common point of origin intersects with Iota Orionis in the Trapezium cluster, some two and half million years in the past. The most likely scenario that could have created these runaway stars is a collision between two binary star systems, with the stars being ejected along different trajectories radial to the point of intersection.^[9]

Etymology

In Chinese astronomy, Mu Columbae is called 屎, Pinyin: Shǐ, meaning "Excrement" or "The Secretions", because this star is marking itself and stand alone in the asterism of the same name within the Three Stars mansion.^[10][11]

References

1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
2. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
3. Sota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J. (2014). "The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars". The Astrophysical Journal Supplement. 211 (1): 10. arXiv:1312.6222. Bibcode:2014ApJS..211...10S. doi:10.1088/0067-0049/211/1/10. S2CID 118847528.
4. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
5. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
6. Aschenbrenner, P.; Przybilla, N.; Butler, K. (2023-03-01). "Quantitative spectroscopy of late O-type main-sequence stars with a hybrid non-LTE method". Astronomy and Astrophysics. 671: A36. arXiv:2301.09462. Bibcode:2023A&A...671A..36A. doi:10.1051/0004-6361/202244906. ISSN 0004-6361.
7. Martins, F.; Schaerer, D.; Hillier, D. J.; Meynadier, F.; Heydari-Malayeri, M.; Walborn, N. R. (2005). "On stars with weak winds: The Galactic case". Astronomy and Astrophysics. 441 (2): 735. arXiv:astro-ph/0507278. Bibcode:2005A&A...441..735M. doi:10.1051/0004-6361:20052927. S2CID 11547293.
8. Walker, Richard (2017), Spectral Atlas for Amateur Astronomers: A Guide to the Spectra of Astronomical Objects and Terrestrial Light Sources, Cambridge University Press, p. 23, ISBN 978-1316738764
9. Gualandris, Alessia; Portegies Zwart, Simon; Eggleton, Peter P. (2004). "N-body simulations of stars escaping from the Orion nebula". Monthly Notices of the Royal Astronomical Society. 350 (2): 615. arXiv:astro-ph/0401451. Bibcode:2004MNRAS.350..615G. doi:10.1111/j.1365-2966.2004.07673.x. S2CID 119024288.
10. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 15 日 Archived 2011-07-16 at the Wayback Machine
11. Richard Hinckley Allen: Star Names — Their Lore and Meaning: Columbae

Further reading

• Blaauw, A.; Morgan, W. W. (1954). "The Space Motions of AE Aurigae and μ Columbae with Respect to the Orion Nebula". Astrophysical Journal. 119: 625. Bibcode:1954ApJ...119..625B. doi:10.1086/145866.
• Hoogerwerf, R.; De Bruijne, J. H. J.; De Zeeuw, P. T. (2001). "On the origin of the O and B-type stars with high velocities. II. Runaway stars and pulsars ejected from the nearby young stellar groups". Astronomy and Astrophysics. 365 (2): 49. arXiv:astro-ph/0010057. Bibcode:2001A&A...365...49H. doi:10.1051/0004-6361:20000014. S2CID 18970167.