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January 20, 2013

Sirius, the brightest star in the night sky, rotates across the south on winter evenings. It’s low in the southeast at nightfall, and it’s hard to miss. Not only is it especially bright, it’s also especially twinkly — it shifts from blue to red to pure white in the blink of an eye.

Sirius is visible from most of Earth’s surface — all but the high Arctic. But the second-brightest star has a more limited range. Canopus is a stunner from the southern hemisphere, but here in the northern hemisphere, it’s tough to see. You have to be south of about Los Angeles or Atlanta to find it. And even then it never climbs more than a few degrees above the horizon.

Canopus itself is quite a bit more impressive than Sirius. It’s far larger and more massive, and about 500 times brighter. But it’s also close to 300 light-years farther, so it can’t quite match Sirius’s luster.

Canopus is at the end of its “normal” lifetime, so it’s quite puffy — if it took the Sun’s place in our own solar system, it would extend all the way out to Mercury. But no one is quite sure whether it’s getting even bigger, or if it’s starting to “deflate” after going through a puffier phase not long ago. Either way, Canopus will continue to shine brightly in Earth’s night sky — even if not everyone can see it.

If you’re far enough south, look for Canopus quite low in the south beginning around 9 o’clock. It’s due south around 10 or 11, almost directly below Sirius.

Script by Damond Benningfield, Copyright 2012

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