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February 21, 2018

When we look at the starry night sky, our eyes and brains play tricks on us. They make us think that if a star is bright, it’s also close by. That’s generally not the case, though. Instead, many of the fainter stars are actually more impressive than some of the brighter ones.

A couple of examples are in Canis Major, the big dog, which is in the south-southeast as night falls at this time of year.

The constellation’s brightest star is Sirius — the brightest star in the night sky. It is a good bit brighter than the Sun. But it looks so bright mainly because it’s quite close.

The dog’s third-brightest star doesn’t look nearly as impressive as Sirius. In reality, though, Wezen is a stellar heavyweight. It looks fainter than Sirius only because it’s almost 200 times farther.

Wezen is about 17 times as massive as the Sun, 200 times wider, and 50,000 times brighter. And it’s also much younger: just 10 million years old, compared to four-and-a-half billion years for the Sun.

You might think that the combination of size and youth would mean that Wezen will be around for a long time. But that’s another bit of stellar trickery. Heavier stars burn through their nuclear fuel at a prodigious rate, so they expire quickly. And in fact, Wezen is already starting to undergo some end-of-life changes. Within a few million years, it’ll explode as a supernova — a big sendoff for one of the leading lights of the big dog.

More about Canis Major tomorrow.

Script by Damond Benningfield

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