So it turns out that everyone’s favourite double star, Albireo, is not a true binary system. The components are about 60 light years apart and simply an optical alignment. This was confirmed by the latest GAIA data release.
Does this news change anything for the average amateur astronomer? Probably not – it’s still the most beautiful double star in the sky! Previous data from Hipparcos had indicated that it probably wasn’t a true binary, but the GAIA data (not particularly user-friendly!) has now confirmed this. Parallax data shows the stars at distances of 100 and 119 parsecs respectively – about 60 light years apart, and their proper motions are completely different too.
Speckle interferometry in the 1970s indicated that the primary orange star may actually be a very close double or even triple system, but this is still not confirmed. Future GAIA releases may be able to shed more light on this.
There are of course other interesting doubles in the Summer sky worth having a look at. Try these two:
Epsilon Lyrae – the double-double star
A telescope is required to separate each star into doubles. All components are yellow-white.
Gamma Delphini
A yellow primary with a greenish secondary. A small telescope will split them.
Finder charts: Cartes du Ciel
Mark Phillips