More Aquarius

StarDate: December 8, 2013

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Most of the stars that look like the Sun are like the Sun. In other words, stars that shine with the same yellowish color as the Sun are about the same size and mass as our home star. But a few oddballs are much bigger and heavier than the Sun, and much later in life. In fact, two of them stand close together in the night sky. They’re the brightest stars of Aquarius, which is where the Moon appears tonight. The stars are to the right of the Moon.

As seen from Earth, Alpha and Beta Aquarii aren’t all that impressive. But that’s only because the stars are hundreds of light-years away. In reality, they’re some of the brightest stars in our part of the galaxy.

Both stars are yellow supergiants. Estimates of their mass say they’re more than six times as heavy as the Sun. And if you dropped either star in the Sun’s place, it would extend out to the orbit of Mercury.

The stars are only about 50 million years old — roughly one percent of the Sun’s age. Yet because they’re so heavy, they’re already nearing the ends of their lives. They’ve burned up the original hydrogen fuel in their cores, and have started to burn the “ashes” of those earlier nuclear reactions. That causes their outer layers to puff outward.

Before long — astronomically speaking — Alpha and Beta Aquarii are likely to expel those outer layers into space. That probably will leave only their hot but dead cores — a pair of white dwarfs shining feebly through the long cosmic night.

 

Script by Damond Benningfield, Copyright 2013

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