Venus, Mars, Aldebaran

StarDate: July 13, 2009

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After hanging out with Mars a few weeks ago, the planet Venus has a new orange companion this week: Aldebaran, the star that represents the eye of Taurus, the bull. And Mars is still around, too.

Venus is the brilliant "morning star." It's the brightest object in the night sky other than the Moon, so you won't have any trouble finding it. Tomorrow, Aldebaran is a little to its lower right. Mars stands above them. It looks almost identical to Aldebaran -- about the same brightness and color.

Aldebaran is about 60 light-years away. If it were like the Sun, we wouldn't see it all. Instead, though, it's like the Sun will be in several billion years: a red giant.

Aldebaran has reached the final stages of life. It burned through the hydrogen in its core to make helium. The core got smaller and hotter, allowing it to start fusing the helium atoms together to make carbon.

The changes in the core caused Aldebaran's outer layers to puff up to many times their previous size. So today, Aldebaran's diameter is about 40 times greater than the Sun's. If Aldebaran took the Sun's place, it would extend half way to the orbit of Mercury, the innermost planet. And from Earth, it would look so big that you'd need both hands to cover it up.

Because of that great size, Aldebaran shines hundreds of times brighter than the Sun, so it's easily visible across 60 light-years of space -- huddling next to Venus for several more days.

Script by Damond Benningfield, Copyright 2009

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