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February 22, 2013

Like some light bulbs, stars shine brightest just before they wink out. Consider the star system known as Procyon, the leading light of Canis Minor, the little dog. It consists of two stars. One of them is nearing the end of its life, so it’s starting to puff up and get brighter. The other has already winked out, leaving behind a hot but tiny cosmic ember.

The first of those stars — known as Procyon A — is a bit bigger and heavier than the Sun, so it shines more brightly. And because of the extra heft, it’s nearing the end of its life even though it’s much younger than the Sun.

The star is about to use up the original hydrogen fuel in its core. As it does so, it’ll begin to burn the hydrogen in a thin shell around the core. That will cause the star’s outer layers to puff outward, making Procyon A shine much brighter than it does now. Eventually, the outer layers will simply puff out into space, leaving behind the star’s tiny, dead core — a white dwarf.

That’s already happened to the system’s other star, Procyon B. The star was born with more mass than Procyon A, so it burned through its nuclear fuel more quickly. Today, it’s a white dwarf. It’s more than half as massive as the Sun, but only about the size of Earth — the burned-out remnant of a once-brilliant star.

Procyon is one of the brightest star systems in the night sky, so it’s easy to pick out. And it’s especially easy to find tonight, because it’s close to the right of the Moon.


Script by Damond Benningfield, Copyright 2012

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