Age, the saying goes, is a state of mind. But for the stars, age is a state of mass — heavier stars live shorter lives.
Consider, for example, Alpha Persei, the brightest star of Perseus, the hero, which is in the northeast at nightfall. The star is probably about 50 million years old — just one percent of the age of the Sun. Yet it’s already nearing the end of its life because it’s probably seven or eight times heavier than the Sun.
A heavy star’s gravity is stronger than that of a more modest star like the Sun. Gravity squeezes the star’s core, making it extremely hot. The high temperature revs up the nuclear reactor that powers the star, so it “burns” through its fuel in a hurry.
Alpha Persei has already used up its original fuel, hydrogen, to make helium. Now, it’s either consuming the helium to make heavier elements, or it’s just about to. Before long, though, this process will come to an end. The star won’t be able to generate enough heat to trigger that next round of nuclear reactions. It most likely will shed its outer layers in a fairly gentle process, leaving behind only its hot but dead core — a white dwarf.
Not surprisingly, massive stars are also big. Alpha Persei is dozens of times wider than the Sun, and thousands of times brighter — so bright that it’s easily visible in the night sky even though it’s 575 light-years away. And it has a lot of siblings that are also easy to see; we’ll have more about that tomorrow.
Script by Damond Benningfield, Copyright 2011
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