Acrux is the brightest star of the Southern Cross, the foot of the cross, a pair of hot blue-white stars that appears on several national flags.
At a glance
| type | blue-white star (class B) |
|---|---|
| distance from the Sun | 322 light-years (98.7 pc) |
| its light left it | 322 years ago |
| luminosity | 51,400 × the Sun |
| radius | 9.92 × the Sun |
| surface temperature | 27,600 K |
| constellation | Crux (Southern Cross) |
Read off the piece’s own catalogue, the same values it draws with.
About Acrux
Acrux is a blue-white star of class B, among the hottest stars visible to the naked eye and outshining the Sun enormously. A small telescope splits it into two bright stars close together, and each of those has companions of its own, so the point the eye sees is a whole family of young, massive stars.
Its name is a modern contraction of its designation, Alpha Crucis, rather than an old Arabic name: the Southern Cross lies too far south to have been seen well from the lands where most traditional star names arose.
Acrux marks the foot of the cross, and the line from Gacrux at the top through Acrux points roughly towards the south celestial pole, which is how southern navigators have used it. With Mimosa, Gacrux and the fainter stars of Crux it appears on the flags of Australia, New Zealand and Brazil, among others.
What you see in the piece
Seen from Earth Acrux and Gacrux are a matched pair at either end of the cross. Fly out and they separate at once: Gacrux is a nearby red star, Acrux a far more distant and powerful blue one.
Measured or modelled
The values on the card describe the system as one star; dividing the light between its members depends on models of each component.
Questions
Why is the Southern Cross used to find south?
The long axis of the cross, from Gacrux through Acrux, points roughly towards the south celestial pole, so following it and dropping to the horizon gives south.
How far away is Acrux?
Acrux is 322 light-years (98.7 pc) from the Sun; its light left it 322 years ago.