Gacrux is the red star at the top of the Southern Cross, a cool, swollen star far wider than the Sun and one of the nearest of its kind.
At a glance
| type | red giant (class M) |
|---|---|
| distance from the Sun | 88.6 light-years (27.2 pc) |
| its light left it | 88.6 years ago |
| luminosity | 1,050 × the Sun |
| radius | 105 × the Sun |
| surface temperature | 3,200 K |
| constellation | Crux (Southern Cross) |
Read off the piece’s own catalogue, the same values it draws with.
About Gacrux
Gacrux is a cool red star of class M, a star that has used up the hydrogen in its core and swollen to a size far greater than the Sun’s. Its surface is cool enough to glow orange-red, and its light is spread over a huge area, which is why it is luminous without being hot.
It is the nearest of the bright stars of Crux by a wide margin, and among the nearest red giants of its type to the Sun. Its name, like that of Acrux, is a modern contraction of its designation, Gamma Crucis.
Gacrux marks the head of the cross. Its warm colour stands out beside the blue-white of Acrux and Mimosa, a contrast visible to the naked eye on a dark night.
What you see in the piece
Its colour is its temperature: in the piece Gacrux is visibly orange-red beside the blue-white stars of the cross. Fly out and it is left far behind them, much closer to the Sun than the rest.
Questions
Why is Gacrux red?
Its surface is cool, about 3,200 K, so it glows red-orange; its great size, 105 × the Sun’s radius, is what makes it luminous.
How far away is Gacrux?
Gacrux is 88.6 light-years (27.2 pc) from the Sun.