Many of the bright stars that decorate the night sky fit a similar profile. They’re roughly twice the size and mass of the Sun, a couple of dozen times its brightness, and only a fraction of its age. The list includes two of the stars of the Summer Triangle, which is high in the sky at nightfall, and the five middle stars of the Big Dipper, which is in the northwest. Another star that fits the profile is in the faint little constellation Lacerta, the lizard, which is in the northeast. Its brightest star is Alpha Lacertae. It’s about a hundred light-years away — far enough to dim some of its luster, so you need dark skies to see it. Like the other stars that fit this profile, Alpha Lacertae is class “A.” That classification is based on its surface temperature, which is thousands of degrees hotter than the surface of the Sun. At that temperature it shines pure white. Alpha Lacertae is around 400 million years old — just one-tenth the age of the Sun. It won’t live anywhere near as long as
