Sheliak is the prototype of a whole class of eclipsing binaries, a pair in Lyra so close that one star pours its gas onto the other.
At a glance
| type | white giant (class A) |
|---|---|
| distance from the Sun | 962 light-years (295 pc) |
| its light left it | 962 years ago |
| luminosity | 3,060 × the Sun |
| radius | 31.4 × the Sun |
| surface temperature | 7,660 K |
| constellation | Lyra (Lyre) |
Read off the piece’s own catalogue, the same values it draws with.
About Sheliak
Sheliak, Beta Lyrae, looks like a single white giant, but it is two stars in a tight orbit. Each passes in front of the other as they circle, and because both are stretched out of round by their mutual pull, its light never stays steady but rises and falls continuously.
The stars are so close that gas streams from the giant onto its companion, which is buried in a thick disc of the gas it has captured. Stars that vary in this smooth, endless way are named Beta Lyrae variables after it.
Its name comes from the Arabic for the harp or lyre. With Sulafat it forms the far side of the small parallelogram below Vega, and between the two lies the Ring Nebula, M57.
What you see in the piece
In the piece it is drawn as one point with the combined light of the pair; the card’s figures describe that light, not either star alone.
Measured or modelled
The hidden companion inside its disc is seen only indirectly, so its nature and size come from models of the system.
Questions
Is Sheliak a variable star?
Yes. It is an eclipsing binary whose brightness changes all the time, and it gives its name to the Beta Lyrae class of variables.
How far away is Sheliak?
Sheliak is 962 light-years (295 pc) from the Sun.