The Giant and the Dwarf

Rising at 11:00 is ruddy Aldebaran, the eye of Taurus the Bull. One of the coolest of the bright stars, its red color tells us it's smoldering at only about four thousand degrees, two thousand degrees cooler than the Sun. But itıs still one of the brightest stars in the sky. That's because it's so big: forty times the diameter of the Sun, its surface -- the part that we see -- is over a thousand times that of the Sun's.

Aldebaran is sixty light years away. That means that just sixty years ago, when many of us were children, the light we see tonight left Aldebaran on its four hundred trillion mile journey.

Circling Aldebaran is a red dwarf companion, a star no bigger than the Earth. Ten thousand times dimmer than Aldebaran, it is visible only in the largest telescopes.

Our Sun is fated to become like each of them in turn, far in the future, when its store of hydrogen fuel becomes depleted.

New fusion reactions will cause it to balloon outward. The Sun will become a giant star, like Aldebaran. Since its limited supply of heat will be spread over its now enormous surface, that surface will be cool. It will become red.

Then, when its fuel is totally gone, gravity will become supreme. The force of gravity will shrink the Sun to a ball the size of the Earth. The Sun will become a dwarf. At first, it will glow white. Then, as it radiates its remaining heat to space, it will become yellow, then red. And then, like a log in a fireplace, it will finally...just wink out.

(09/10/08)