Albireo marks the head of Cygnus, the swan, and is one of the loveliest sights in a small telescope: a golden star beside a blue one.
At a glance
| type | orange giant (class K) |
|---|---|
| distance from the Sun | 434 light-years (133 pc) |
| its light left it | 434 years ago |
| luminosity | 1,470 × the Sun |
| radius | 60.4 × the Sun |
| surface temperature | 4,600 K |
| constellation | Cygnus (Swan) |
Read off the piece’s own catalogue, the same values it draws with.
About Albireo
The bright member is an orange giant of class K, a star that has left the main sequence and swollen to many times the Sun’s width, cooling at the surface as it grew. A small telescope shows a fainter companion close beside it, distinctly blue, and the contrast of the two colours is the reason Albireo is a favourite target.
The colours are honest: the giant is cool and the companion is a hot, fast-spinning blue star. The giant itself turns out to be a close pair as well. Albireo sits at the foot of the Northern Cross, the long axis of which runs from here through Sadr to Deneb.
Its name is a tangle of translation. It did not come from a real Arabic word; it grew out of medieval Latin and Arabic renderings of the old description of the star as the bird’s beak, garbled along the way into a form that stuck.
What you see in the piece
In the piece the colour of each star is its temperature, so the golden giant and its blue companion keep the contrast you see through a telescope. Fly close and the pair separate into two distinct suns.
Measured or modelled
Whether the blue companion is truly bound to the golden giant or is simply in the same line of sight is debated: measurements of their distances and motions have been read both ways.
Questions
Why is Albireo two colours?
Albireo is a pair: a cool orange giant and a hotter blue companion close beside it on the sky. Each shows the colour of its own surface temperature.
How far away is Albireo?
The bright star of Albireo is 434 light-years (133 pc) from the Sun.