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The Little Dog

January 28, 2012

The big dog trots across the southern sky on winter nights — the constellation Canis Major. It’s conspicuous for its leading light — Sirius, the Dog Star, which is the brightest star in the night sky. It’s low in the southeast at nightfall, and well up in the south in late evening.

Canis Major is escorted across the sky by the little dog, Canis Minor, which is to the upper left of the big dog in early evening.

If you have a fairly dark sky, it’s not hard to see Canis Major as a four-legged animal. But Canis Minor is another story. On most starcharts, it’s drawn as a single line connecting two stars.

One of those is quite easy to spot, though, because it’s also one of the brightest stars in the night sky: Procyon, a star whose name means “before the dog.” The name indicates that from mid- to high-northern latitudes, which includes most of the United States, Procyon rises before Sirius.

Like Sirius, Procyon is a close neighbor — a bit more than 11 light-years away. The star itself is similar to Sirius, so it’s bigger, hotter, and brighter than the Sun. And also like Sirius, it has a “dead” companion — a crushed stellar core known as a white dwarf. The original star was more massive than Procyon, so it burned out more quickly. The companion is too faint to see without a telescope. And even with a telescope, it’s so close to Procyon that it’s quite difficult to spot through the glare.

We’ll have more about the big dog tomorrow.


Script by Damond Benningfield, Copyright 2011


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