Achernar is the bright blue-white star at the end of the river Eridanus, spinning so fast that it is one of the flattest stars ever measured.
At a glance
| type | blue-white star (class B) |
|---|---|
| distance from the Sun | 139 light-years (42.8 pc) |
| its light left it | 139 years ago |
| luminosity | 3,150 × the Sun |
| radius | 7.3 × the Sun |
| surface temperature | 15,000 K |
| constellation | Eridanus (River) |
Read off the piece’s own catalogue, the same values it draws with.
About Achernar
Achernar is a hot, massive main-sequence star, far more luminous than the Sun. Its name comes from Arabic for the end of the river, since it marks the southern end of the long, winding constellation of Eridanus.
Its rotation is close to the speed at which a star would begin to fly apart at the equator. Interferometers have measured its shape and found it strongly flattened, much wider across the equator than through the poles. It is a Be star: from time to time it sheds gas from its equator into a thin surrounding disc, which shows up as bright emission lines in its spectrum.
What you see in the piece
With HUMAN EYE on from the south it is a bright blue-white point in a sparse region of sky; from much of the northern hemisphere it never rises. Close up it is a hot blue-white disc.
Questions
Why is Achernar so flat?
It spins so fast that its equator bulges far outwards; interferometers have shown it to be one of the most flattened stars known.