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The big dog is best known for the Dog Star, Sirius — the brightest star in the night sky. But many of Canis Major’s bright stars are actually far more impressive than Sirius. They look fainter only because they’re much farther away.

A prime example is Adhara, the constellation’s second-brightest star. Although it looks only a few percent as bright as Sirius, it’s actually thousands of times brighter. But it’s more than 400 light-years farther, which dims its luster.

Adhara is already one of the more impressive stars in the galaxy. It’s 10 times the Sun’s mass, and more than 10 times its diameter. Such heavy stars “burn” through the nuclear fuel in their cores in a hurry, so they produce huge amounts of energy.

Yet Adhara is about to get even more impressive.

It’s at the end of its “normal” lifetime. It’s consumed the original hydrogen fuel in its core, converting it to helium. Now, it’s getting ready to burn the helium to make even heavier elements. As a result, it’ll soon get much bigger, and shine many times brighter. And at the end of its life, the star will get more impressive still: It will explode as a supernova. For a few weeks or months, it’ll outshine billions of normal stars — making Sirius look like a flickering candle by comparison.

Sirius is low in the southeast at nightfall. It’s so bright, though, that it’s easy to find. Adhara perches below it, forming one of the legs of the big dog.

Tomorrow: celebrations of spring.


Script by Damond Benningfield

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