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Moon and Aldebaran
For the most part, trying to foretell the future just doesn't work. But there's one group for which the future is ordained in the stars: the stars themselves -- especially single stars like our Sun. Just from a star's mass, astronomers can tell us how the star will age and how it will die. And they can even tell us when -- on an astronomical time scale, anyway.
For example, they know that in a few billion years, the Sun will consume the hydrogen fuel in its core. It'll puff up to dozens of times its current diameter, so its surface will get much cooler. From its nearby neighbors, it'll look like a bright orange gemstone against the black setting of the night sky.
In fact, it'll look a lot like the star Aldebaran does now. It's the orange "eye" of Taurus, the bull. It's close to the left of the Moon this evening.
Aldebaran is well into the "giant" phase of its life. It's converted the hydrogen in its core to helium, and is now burning the helium to make even heavier elements. That's made its core much hotter, so it produces more radiation to puff up its outer layers.
Eventually, Aldebaran will shed those outer layers, creating a beautiful shell of gas and dust. Over many thousands of years, the shell will drift away into space, leaving only the star's hot, dense core -- a white dwarf. Over billions of years, this tiny stellar corpse will slowly cool and fade away -- a fate that's foretold in the stars.
Script by Damond Benningfield, Copyright 2011
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