| absmag_v =
}}{{Starbox detail
| component1 = A
| age = {{nowrap|8 to 11 million}}[5]
| metal_fe = –0.08[15]
| gravity = {{nowrap|3.6 ± 0.1}}[5]
| mass = 16[5]
| radius = {{nowrap|8.4 ± 0.6}}[5]
| rotational_velocity = 35[5]
| rotation = 3.6 days[5]
| luminosity = 34,000[5]
| temperature = {{nowrap|27,000 ± 1,000}}[5]
| component2 = B
| mass2 = 10[6]
}}{{Starbox visbin
| name = β Cru B
| reference = [6]
| period_unitless = 1828.0 ± 2.5 days
| axis_unitless = 8.7 AU
| eccentricity = 0.38 ± 0.09
| inclination =
| node =
| periarg = 293 ± 9
| periastron = 2449879 ± 38
}}{{Starbox catalog
| names=Mimosa,[25] Becrux,[26] β Crucis, HR 4853, CPD−59°4451, HD 111123, FK5 481, SAO 240259, HIP 62434
}}{{Starbox reference
| Simbad=HD+111123
}}{{Starbox end}}Beta Crucis (Latinised from β Crucis, abbreviated Beta Cru, β Cru), also called Mimosa,[25] is a binary star system; the second-brightest object in the constellation of Crux (after α Crucis or Acrux) and the 19th-brightest star in the night sky. It forms part of the prominent asterism called the Southern Cross.
Nomenclature
β Crucis (Latinised to Beta Crucis) is the system's Bayer designation. Although β Crucis is at roughly −60° declination, and therefore not visible north of 30° latitude, in the time of the ancient Greeks and Romans it was visible north of 40° due to the precession of equinoxes, and these civilizations regarded it as part of the constellation of Centaurus.[28]It bore the traditional names Mimosa and the historical name Becrux. Mimosa, which is derived from the Latin for 'actor', may come from the flower of the same name.[29] Becrux is a modern contraction of the Bayer designation.[26] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[2] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[3] included a table of the first two batches of names approved by the WGSN; which included Mimosa for this star.
In Chinese, {{lang|zh|十字架}} ({{lang|zh-Latn|Shí Zì Jià}}), meaning Cross, refers to an asterism consisting of α Crucis, β Crucis, γ Crucis, and δ Crucis.[4] Consequently, β Crucis itself is known as {{lang|zh|十字架三}} ({{lang|zh-Latn|Shí Zì Jià sān}}, {{lang-en|the Third Star of Cross}}.).[5]
Stellar system
Based on parallax measurements, β Crucis is located at a distance of {{Convert|280|ly|pc|abbr=on|lk=on}} 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.[35] 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 {{nowrap|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 {{nowrap|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. 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.[39] It is generating a strong stellar wind and is losing about {{solar mass|10−8|link=yes}} 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.[42] This is a stellar association of stars that share a common origin.[5]
In culture
β Crucis is represented in the flags of Australia, New Zealand, Samoa and Papua New Guinea as one of five stars making up the Southern Cross.[5] It is also featured in the flag of Brazil, along with 26 other stars, each of which represents a state. Mimosa represents the State of Rio de Janeiro.[6]
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.{{cn|date=November 2017}}
References
1. ^{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)|journal=VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S|volume=1|pages=02025|author1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009|display-authors=etal}}
2. ^{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|accessdate=22 May 2016}}
3. ^{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 1 |accessdate=28 July 2016}}
4. ^{{zh icon}} 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, {{ISBN|978-986-7332-25-7}}.
5. ^{{zh icon}} 香港太空館 - 研究資源 - 亮星中英對照表 {{webarchive|url=https://web.archive.org/web/20110130063012/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_m.htm |date=2011-01-30 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.
6. ^{{cite web|title=Astronomy of the Brazilian Flag|url=https://flagspot.net/flags/br_astro.html|publisher=FOTW Flags Of The World website}}
7. ^1 {{citation | last=Kilian | first=J. | title=Chemical abundances in early B-type stars. 5: Metal abundances and LTE/NLTE comparison | journal=Astronomy and Astrophysics | volume=282 | issue=3 | pages=867–873 |date=February 1994 | bibcode=1994A&A...282..867K }}
8. ^1 {{cite conference | last1=Evans | first1=D. S. | date=June 20–24, 1966 | editor1-last=Batten | editor1-first=Alan Henry | editor2-last=Heard | editor2-first=John Frederick | contribution=The Revision of the General Catalogue of Radial Velocities | title=Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30 | journal=Determination of Radial Velocities and their Applications | volume=30 | pages=57 | location=University of Toronto | publisher=International Astronomical Union | bibcode=1967IAUS...30...57E }}
9. ^1 2 3 {{citation | last1=Johnson | display-authors=1 | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | pages=99 | date=1966 | bibcode=1966CoLPL...4...99J }}
10. ^1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 {{citation | display-authors=1 | last1=Cohen | first1=David H. | last2=Kuhn | first2=Michael A. | last3=Gagné | first3=Marc | last4=Jensen | first4=Eric L. N. | last5=Miller | first5=Nathan A. | title=Chandra spectroscopy of the hot star βCrucis and the discovery of a pre-main-sequence companion | journal=Monthly Notices of the Royal Astronomical Society | volume=386 | issue=4 | pages=1855–1871 |date=June 2008 | doi=10.1111/j.1365-2966.2008.13176.x | bibcode=2008MNRAS.386.1855C |arxiv = 0802.4084 }}
11. ^1 {{citation | last1=Heintz | first1=W. D. | title=The radial velocity variation of beta Crucis | journal=The Observatory | volume=77 | page=200 |date=October 1957 | bibcode=1957Obs....77..200H }}
12. ^1 2 3 4 5 {{citation | display-authors=1 | last1=Aerts | first1=C. | last2=De Cat | first2=P. | last3=Cuypers | first3=J. | last4=Becker | first4=S. R. | last5=Mathias | first5=P. | last6=De Mey | first6=K. | last7=Gillet | first7=D. | last8=Waelkens | first8=C. | title=Evidence for binarity and multiperiodicity in the beta Cephei star beta Crucis | journal=Astronomy and Astrophysics | volume=329 | pages=137–146 |date=January 1998 | bibcode=1998A&A...329..137A }}
13. ^1 2 {{cite book|bibcode=1991bsc..book.....H|title=The Bright star catalogue|journal=New Haven|author1=Hoffleit|first1=Dorrit|last2=Jaschek|first2=Carlos|year=1991}}
14. ^1 2 {{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |accessdate=28 July 2016}}
15. ^1 {{citation | title=MIMOSA (Beta Crucis) | work=Stars | publisher=university of Illinois | url=http://www.astro.uiuc.edu/~kaler/sow/mimosa.html | accessdate=2011-12-30 | deadurl=yes | archiveurl=https://web.archive.org/web/20051222141734/http://www.astro.uiuc.edu/~kaler/sow/mimosa.html | archivedate=2005-12-22 | df= }}
16. ^1 {{citation |title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |accessdate=2012-01-16 |deadurl=yes |archiveurl=https://www.webcitation.org/6630AbtJZ?url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archivedate=2012-03-10 |df= }}
17. ^1 {{citation | last1=Rizzuto | first1=Aaron | last2=Ireland| first2=Michael | last3=Robertson | first3=J. G. | title=Multidimensional Bayesian membership analysis of the Sco OB2 moving group | journal=Monthly Notices of the Royal Astronomical Society |date=October 2011 | volume=416 | issue=4 | pages=3108–3117 | doi=10.1111/j.1365-2966.2011.19256.x | bibcode=2011MNRAS.416.3108R | arxiv=1106.2857 | postscript=. }}
18. ^1 {{citation | first1=Susan | last1=Wilkinson | title=Mimosa: The Life and Times of the Ship That Sailed to Patagonia | publisher=Y Lolfa | date=2007 | isbn=0-86243-952-3 | pages=56–57 | url=https://books.google.com/books?id=OscUpqaBzPoC&pg=PA56 }}