by Bill Murmann
During the summer, one of the best colorful double stars is Albireo, the head of the “Swan” in the constellation Cygnus. “Double Stars” was the topic for the program at our monthly meeting on Monday, September 12, and Albireo is a great example. Albireo is 380 light years away; the pair of stars is designated “Albireo A” and “Albireo B.”
Albireo A is yellow star, slightly cooler than our Sun. It has a surface temperature estimated at 7,000 degrees F., compared to the Sun’s 9,000-degree F. surface temperature.
Its companion, Albireo B, is a hot, blue star with an estimated surface temperature of about 23,000 degrees F. It also rotates very fast — at about 560,000 MPH.
When we are looking at Albireo, we are actually seeing three stars. Albireo A is, itself, a close binary star. Most of us, however, can’t split this pair with our telescopes. It takes a minimum 20-inch telescope under really good sky conditions to split Albireo A. Paul Leopold with his 20-inch scope is probably the only CAA member who has a chance to see all three stars in Albireo.