Beta Crucis

β Cru A/B

Observation data Epoch J2000      Equinox J2000
Constellation	Crux
Right ascension	12h 47m 43.2s
Declination	−59° 41' 19"
Apparent magnitude (V)	1.30
Characteristics
Spectral type	B0.5 IV
U−B color index	−1.00
B−V color index	−0.15
Variable type	Beta Cephei
Astrometry
Radial velocity (Rv)	+15.6 km/s
Proper motion (μ)	RA: −48.24 mas/yr Dec.: −12.82 mas/yr
Parallax (π)	9.25 ± 0.61 mas
Distance	350 ± 20 ly (108 ± 7 pc)
Absolute magnitude (MV)	−3.92
Details
Mass	14 M☉
Radius	8 R☉
Luminosity	34,000 L☉
Temperature	28,200 K
Metallicity	80% Sun
Age	10 million years
Orbit
Companion	β Cru B
Period (P)	4.0 yr
Semimajor axis (a)	8.0 AU"
Eccentricity (e)	0
Inclination (i)	0°
Longitude of the node (Ω)	0°
Periastron epoch (T)	0
Other designations
Mimosa, Becrux, β Crucis, HR 4853, CPD P-59°4451, HD 111123, FK5 481, SAO 240259, HIP 62434.
Database references
SIMBAD	data

Mimosa or Becrux (β Cru, β Crucis, Beta Crucis) is the second brightest star in the constellation Crux (after Alpha Crucis or Acrux) and is one of the brightest stars in the night sky.

Beta Crucis is located approximately 350 light years away from Earth. It is a spectroscopic binary with components that are too close together to resolve with a telescope. The pair orbit each other every 5 years and are separated by about 8 AU. Beta Crucis, being of spectral type B0.5IV, is believed to be the hottest first-magnitude star.

Since Beta Crucis, "Becrux", is at roughly −60° declination, it is only visible south of the Tropic of Cancer and did not therefore receive a traditional name, "Mimosa" being a recent name based on its color.

In Chinese, 十字架 (Shí Zì Jià), meaning Cross, refers to an asterism consisting of β Crucis, γ Crucis, α Crucis and δ Crucis.^[1] Consequently, β Crucis itself is known as 十字架三 (Shí Zì Jià sān, English: the Third Star of Cross.).^[2]

Modern legacy

Mimosa is represented in the flags of Australia, New Zealand and Papua New Guinea as one of five stars making up the Southern Cross. 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^[3] .

External links

• "MIMOSA". Stars. http://www.astro.uiuc.edu/~kaler/sow/mimosa.html. Retrieved November 28, 2005. 
• http://jumk.de/astronomie/big-stars/becrux.shtml

References

1. ^ (Chinese) 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.
2. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
3. ^ "Astronomy of the Brazilian Flag". FOTW Flags Of The World website. http://www.fotw.net/flags/br_astro.html.