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A thin wedge of stars climbs the eastern sky on November evenings. It fills an otherwise dark space between the well-known constellations Aries, Perseus, and Andromeda. None of its stars is all that bright, but the distinctive triangular pattern will help you pick it out.
Triangulum is just slightly north of due east as darkness falls, lining up roughly parallel to the horizon. Its brightest star, Beta Trianguli, is at the top left corner of the triangle, with the second-brightest star well to the right, forming the tip of the wedge.
Both of those stars are actually double — two stars locked in tight orbits. The primary star of each system is nearing the end of its life. The stars are using up the last of the hydrogen fuel in their cores, “fusing” the hydrogen atoms together to make helium. As they finish that process, their outer layers are puffing up. So each star is several times wider than the Sun, and quite a bit brighter. Over millions of years, they’ll start to burn the helium, so they’ll get even bigger and brighter.
And as they get close to the ends of their lives, they’ll become unstable, so they’ll puff in and out like a beating heart. In fact, another star in Triangulum is already doing just that. Known as R Trianguli, it’s to the lower left of Beta.
Don’t bother looking for it, though, because it’s not bright enough to see with the unaided eye. It will be just bright enough to see in a few months, though; more about that tomorrow.
Script by Damond Benningfield, Copyright 2012