The Sun is about halfway through its “normal” lifetime — the period when it sedately consumes the hydrogen fuel in its core to make helium. When the hydrogen is all gone, it’ll go through a series of dramatic changes. It’ll puff up to many times its current size, and shine dozens of times brighter. And its surface will cool, making it look orange.
In other words, it’ll look a lot like the star Aldebaran does now. Aldebaran is the bright “eye” of Taurus, the bull. It’s close to the lower right of the Moon as they rise shortly before midnight tonight, and stays with the Moon as they climb high up the southern sky in the wee hours of the morning.
Aldebaran has finished its normal lifetime, and is puffing up to become a red giant. Right now, it’s about 40 times wider than the Sun, and about 40 times brighter. Over the next few million years, though, it’ll get even bigger and brighter. Eventually, it’ll shine hundreds of times brighter than the Sun.
Compared to the star’s overall lifetime, though, this showiness won’t last for long — no more than a few hundred million years. After that, it’ll briefly puff up even more, then slough off its outer layers. For awhile, the escaping gas will form a beautiful cloud known as a planetary nebula. As the nebula dissipates, only the star’s dead but superhot core will remain — a white dwarf.
It’s the same fate that awaits the Sun — billions of years in the future.
Script by Damond Benningfield, Copyright 2011