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Moon and Aldebaran

December 23, 2015

The bull gets an eyeful of moonlight tonight. Aldebaran, the bright star that represents the eye of Taurus, stands close to the upper right of the Moon at nightfall, and the two remain close throughout the night.

Aldebaran is one of many stars visible to our own eyes that show us something special: the fate of our own Sun.

For most of its life, Aldebaran was similar to the present-day Sun — a main-sequence star. Such a star steadily “fuses” atoms of hydrogen in its core to make helium, the next-heavier element.

When the hydrogen is gone, the core goes through a series of changes. Those changes cause the star’s outer layers to puff up like a giant balloon. The star gets many times wider, so it moves off the main sequence and into the “giant” phase of life.

Because the outer layers are so puffy, they also get cooler. In fact, Aldebaran is thousands of degrees cooler than the Sun. At that temperature, the surface shines a dull orange. It’s tough to see that color tonight, with the Moon nearby. But after the Moon moves away, you shouldn’t have any trouble detecting the color in the bull’s eye.

The Sun will remain on the main sequence for several billion years. After that, it, too, will begin to enter the giant phase. That phase will last for a billion years or so before the final phase: The Sun will cast its outer layers into space, leaving only its hot but dead core — a fate that’s not far away for beautiful Aldebaran.


Script by Damond Benningfield, Copyright 2015

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