It bore the traditional names Mimosa and the historical name Becrux/ˈbeɪkrʌks/.[13]Mimosa, which is derived from the Latin for 'actor', may come from the flower of the same name.[14]Becrux is a modern contraction of the Bayer designation.[10] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[16] included a table of the first two batches of names approved by the WGSN; which included Mimosa for this star.
InChinese, 十字架 (Shí Zì Jià), meaning Cross, refers to an asterism consisting of Acrux, Mimosa, Gamma Crucis, and Delta Crucis.[17] Consequently, Mimosa itself is known as 十字架三 (Shí Zì Jià sān, English: the Third Star of Cross.).[18]
Based on parallax measurements, Mimosa is located at a distance of 280 ly (86 pc) from the Earth. In 1957, German astronomer Wulff-Dieter Heintz discovered that it is a spectroscopic binary with components that are too close together to resolve with a telescope.[19] The pair orbit each other every 5 years with an estimated separation that varies from 5.4 to 12.0 Astronomical Units.[6] The system is only 8 to 11 million years old.[5]
The primary, β Crucis A, is a massive star with about 16 times the Sun's mass. The projected rotational velocity of this star is about 35 km s−1. However, the orbital plane of the pair is only about 10°, which probably means the inclination of the star's pole is also likely to be low. This suggests that the azimuthal rotational velocity is quite high, at about 120 km s−1. With a radius of about 8.4 times the radius of the Sun, this would mean the star has a rotational period of only about 3.6 days.[5]
β Crucis A is a known β Cephei variable, although with an effective temperature of about 27,000 K it is at the hot edge of the instability strip where such stars are found. It has three different pulsation modes, none of which are radial. The periods of all three modes are in the range of 4.03–4.59 hours. Owing to the first application of polarimetry it is the heaviest star with an age determined by asteroseismology.[21] The star has a stellar classification of B0.5 III, with the luminosity class of 'III' indicating that this is a giant star that has exhausted the supply of hydrogen at its core. The high temperature of the star's outer envelope is what gives the star the blue-white hue that is characteristic of B-type stars.[22] It is generating a strong stellar wind and is losing about 10−8M☉ per year, or the equivalent of the mass of the Sun every 100 million years. The wind is leaving the system with a velocity of 2,000 km s−1 or more.[5]
The secondary, β Crucis B, may be a main sequence star with a stellar class of B2.[6] In 2007, a third companion was announced, which may be a low mass, pre-main sequence star. The X-ray emission from this star was detected using the Chandra X-ray Observatory. Two other stars, located at angular separations of 44 and 370 arcseconds, are likely optical companions that are not physically associated with the system. The β Crucis system may be a member of the Lower Centaurus–Crux sub-group of the Scorpius–Centaurus association.[23] This is a stellar association of stars that share a common origin.[5]
A vessel named MV Becrux is used to export live cattle from Australia to customers in Asia. An episode dedicated to the vessel features in the television documentary series Mighty Ships.[25]
^ abcJohnson, 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
^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: 02025. Bibcode:2009yCat....102025S.
^ abcdeAerts, C.; et al. (January 1998), "Evidence for binarity and multiperiodicity in the beta Cephei star beta Crucis", Astronomy and Astrophysics, 329: 137–146, Bibcode:1998A&A...329..137A
^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. Determination of Radial Velocities and Their Applications. Vol. 30. University of Toronto: International Astronomical Union. p. 57. Bibcode:1967IAUS...30...57E.
^Kilian, J. (February 1994), "Chemical abundances in early B-type stars. 5: Metal abundances and LTE/NLTE comparison", Astronomy and Astrophysics, 282 (3): 867–873, Bibcode:1994A&A...282..867K
^ abHoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven. Bibcode:1991bsc..book.....H.
^"The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16
^"Mighty Ships". DiscoveryHD.ca. CTV Global Media. Archived from the original on 15 September 2008. Retrieved 25 November 2013.{{cite web}}: CS1 maint: unfit URL (link)
12h47m43.26877s, −59° 41′ 19.5792″
