The Dog’s Tail

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The Dog’s Tail

The hindquarters of the big dog face a painful future. The stars that outline his tail and back legs are destined to explode within the next few million years.

Canis Major, the big dog, clears the southeastern horizon by about 9 o’clock. The brightest star in all the night sky, Sirius, is at the front of the dog. The hindquarters are outlined by a triangle of three moderately bright stars well below Sirius: Wezen at the top of the triangle, Adhara to its right or lower right, and Aludra, the faintest of the three, at the bottom.

The stars are quite similar. They’re all much bigger, brighter, and hotter than the Sun, and more than 10 times heavier. And they’re all in about the same stage of life. They’ve used up the hydrogen fuel in their cores to make helium, so the fusion reactions in their cores have stopped.

Now, the cores are shrinking and getting hotter, so they’re about to start fusing the helium to make oxygen and carbon. As that happens, the stars will get even bigger and brighter.

And all three stars likely face the same fate. Within a few million years, they’ll all reach a point where they can no longer sustain any reactions. When that happens, each star’s core will collapse, and its outer layers probably will explode as a supernova.

Although it looks fainter than the other two, the most impressive of the three stars appears to be Aludra, at the tip of the dog’s tail. More about that tomorrow.

Script by Damond Benningfield

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