You are here


July 6, 2013

The three bright stars that outline the Summer Triangle really stand out this weekend. There’s no Moon in the sky, so Vega, Deneb, and Altair don’t have to compete with its glare. The triangle is low in the east and northeast as darkness falls, but wheels high overhead during the night.

With the Moon out of the way, many of the stars inside the triangle are in good view as well.

One of the most popular is Albireo, the fifth-brightest star of Cygnus, the swan. To the eye alone, it looks like a single modest star. But binoculars or a telescope reveal two stars. One looks yellow-orange, while the other is sapphire blue. A nineteenth-century writer said this combination presents, quote, perhaps the most lovely effect of colour in the heavens.

The colors reveal the surface temperatures of Albireo’s stars. The yellow-orange star is cooler than our own star, the Sun. It’s a stellar giant, which means it’s many times larger than the Sun. The blue star, on the other hand, is much hotter than the Sun. Blue stars “burn” their nuclear fuel much more quickly than other stars, so they live shorter lifetimes.

The stars of Albireo are about 380 light-years from Earth. That means the light we see from Albireo tonight actually began its trek through space almost a century-and-a-half before the birth of the United States.

Look for Albireo a little below Vega, the brightest and highest member of the Summer Triangle, beginning as twilight fades from the evening sky.


Script by Damond Benningfield, Copyright 2013

Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.