Like so many astronomical objects, double and multiple stars can be enjoyed on many levels. Their aesthetic beauty is more than enough for some - the contrast between stars of different magnitude or between different colours, and the sheer astonishment of seeing those two pinpricks of light and knowing that if we were alien observers on a planet in their solar system there would be two suns in our sky.

One of the most beautiful doubles is the famous northern hemisphere star Albireo (Beta Cygni). The colour contrast is absolutely spectacular, with the brighter (primary) star yellow and the secondary bright blue. And then you can experience the subjective nature of assessing colour in stars ! The eye is not good at perceiving colour in low light conditions so there is sometimes disagreement amongst visual observers. In the books listed below, Hartung calls them “deep yellow and pale bluish”, Burnham “golden yellow or topaz, and sapphire”, Norton’s “yellow and greenish (by contrast)”, Menzel and Pasachoff “yellow and green”, and the recent book by James Mullaney “orange and blue” in a photograph of the pair. So take your pick. What do you see ? It’s said to be resolvable in steadily held binoculars, with a separation of 35 seconds of arc.

And there are a surprising number of doubles with this particular colour combination visible in the southern hemisphere, including Beta Capricorni, h3945 Canis Majoris, and Iota Cancri.