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Alpha Lacertae

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 Lacerta, the lizard, which is half way up the northeastern sky. The faint little constellation’s 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’s based on its surface temperature, which is thousands of degrees higher than the surface of the Sun. At that temperature, the star shines pure white.

Alpha Lacertae is about 400 million years old — just one-tenth the age of the Sun. It won’t live nearly as long as the Sun will, because it’s more than twice as massive as the Sun. Its gravity squeezes its core tightly, revving up its nuclear reactions. So Alpha Lacertae will live a “normal” lifetime of only a couple of billion years, versus about 10 billion years for the Sun.

After that, it’ll cast its outer layers into space, briefly surrounding its dead core with a bubble of gas — bringing its fairly short life to a colorful end.

Script by Damond Benningfield

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