The brighter star, Albireo A, is in fact a binary, with a red giant (called Albireo Aa), in orbit with a blue main sequence star, one still fusing hydrogen into helium in its core (called Albireo Ac; the letter b was skipped so it wouldn't be confused with Albireo B, the other star seen in small telescopes).

What kind of star is Albireo A?

Key Facts & Summary

Albireo Aa is a bright-yellow giant star of spectral type K2II. It has an apparent magnitude of 3.18 and an absolute magnitude of -2.45. Albireo Aa has around 14.52 solar masses and a radius of around 69 times that of the Sun.

What type of object is Albireo?

Albireo is a showpiece double star and one of the great small telescope objects. To the naked eye, it's the fifth brightest star in Cygnus (combined mag. +2.9) and the lone star that marks the head of "the Swan" constellation.