name=Acrux AB Starbox image
caption=The position of Acrux. Starbox observe
ra=12h 26m 35.8958s
dec= -63° 05' 56.73"
appmag_v=0.81 Starbox character
variable=? Starbox astrometry
absmag_v=0.56 Starbox detail
mass=14 / 10
temperature= 28.000 Starbox visbin
periastron= Starbox reference
Acrux (α Cru / α Crucis / Alpha Crucis) is the brightest star in
constellation Crux, the Southern Cross and, at visual magnitude0.77, is the twelfth brightest star in the night time sky. Acrux is the southernmost first-magnitude star, just a bit more southerly than Alpha Centauri.
Acrux is a
multiple starlocated 321 light yearsfrom the solar system. Only two components are visually distinguishable, α1 and α2, separated by 4 arcseconds. α1 is magnitude 1.40 and α2 is magnitude 2.09, both hot class B (almost class O) stars, with surface temperatures of about 28,000 and 26,000 kelvins respectively. Their luminosities are 25,000 and 16,000 times that of the Sun. α1 and α2 orbit over such a long period that motion is only barely seen. From their minimum separation of 430 astronomical units, the period is at least 1,500 years, and may be much longer.
name=Acrux CA Starbox image
caption=System Acrux. Starbox observe
ra=12h 26m 35.871s
dec=-63° 05' 56.58"
appmag_v=1.4 Starbox character
b-v=−0.08 Fact|date=July 2008
variable=? Starbox astrometry
absmag_v=1.32 Starbox detail
temperature= 26.000 Starbox visbin
periastron= Starbox catalog
names=α1 Crucis/α2 Crucis, HR 4730/4731, CD -62°2745, HD 108248/108249, SAO 251904, FK5 462, HIP 60718. Starbox reference
α1 is itself a
spectroscopic binarystar, with its components thought to be around 14 and 10 times the mass of the Sun and orbiting in only 76 days at a separation of about 1 AU. The masses of α2 and the brighter component of α1 suggest that the stars will someday explode as supernovae. The fainter component of α1 may survive to become a massive white dwarf.
Another class-B subgiant lies 90 arcseconds away from triple Acrux and shares Acrux's motion through space, suggesting it may be gravitationally bound to Acrux. However, if it is indeed located near Acrux, it is under-luminous for its class. It is probably just an optical
double star, most likely several hundred light years beyond Acrux.
"Acrux" is simply a contraction of the "A" in Alpha plus Crux.
Since Acrux is at roughly −60° declination, it is only visible south of the
Tropic of Cancer. Because of Earth's axial precession, however, the star was visible to ancient Hindu astronomers in India who named it “Tri-shanku”.
It is known as 十字架二 (the Second Star of the Cross) in Chinese.
Acrux is represented in the flags of Australia and New Zealand as one of five stars which comprise the
Southern Cross. It is also featured in the flag of Brazil, along with 26 other stars, each of which represents a state. Acrux represents the State of São Paulo.
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