Albireo B is the blue star of Albireo’s famous gold-and-blue pair, a hot rapidly spinning star that sits beside the orange giant in any small telescope.
At a glance
| type | blue-white star (class B) |
|---|---|
| distance from the Sun | 434 light-years (133 pc) |
| its light left it | 434 years ago |
| luminosity | 230 × the Sun |
| radius | 2.7 × the Sun |
| surface temperature | 13,200 K |
Read off the piece’s own catalogue, the same values it draws with.
About Albireo B
Albireo is one of the most admired double stars in the sky because of its colours: the orange giant and, beside it, Albireo B, a blue-white B-type star. The contrast is real: the colours are the temperatures of the two stars, one cool, one hot.
Albireo B spins very fast and is classed as a Be star, the kind that throws off a disc of gas around its equator; that gas adds emission lines to its spectrum.
For a long time the two were assumed to orbit each other. Precise measurements of their positions and motions, especially from the Gaia mission, have reopened the question: the two stars appear to move differently enough that they may be an unrelated pair seen in the same direction.
What you see in the piece
Fly to Albireo and B shows as a blue-white star apart from the orange giant; the contrast between them is the contrast in their temperatures.
Measured or modelled
Whether Albireo B is gravitationally bound to Albireo A or only lies along the same line of sight is not settled; the card places them at the same distance.
Questions
Are the two stars of Albireo really a pair?
Possibly not. Their motions measured by Gaia differ enough that astronomers debate whether Albireo B orbits the golden star or is just in the same direction.
Why is Albireo B blue?
Its colour is its temperature: its surface is about 13,200 K, much hotter than the orange giant beside it.