StarDate: February 23, 2009

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Leo climbs proudly up the eastern sky this evening. It's in full view by about 8 o'clock. Its brightest star, Regulus, is high in the sky by then, well above the golden planet Saturn. And the lion's tail is a little to the left of Saturn.

The tail is represented by a star named Denebola. It's about twice as big as the Sun, and twice as massive. The extra heft makes it "burn" through the hydrogen in its core much faster than the Sun does. And that, in turn, makes its surface thousands of degrees hotter than the Sun's.

Astronomers use surface temperature as part of their system for classifying stars. They use the letters O-B-A-F-G-K and M to represent different temperature levels, which have different colors. Class "O" stars are the hottest, so they shine blue-white. "M" stars are the coolest, so their surfaces look orange or even red. The Sun is on the cooler side of the scale, at class G. Denebola's on the hotter end, at class A.

Because of its higher temperature and its greater size, Denebola shines about 15 times brighter than the Sun. That's the reason it's easily visible to the unaided eye. From Denebola's distance of around 40 light-years, the Sun would barely register.

A faint disk of dust grains encircles Denebola -- the raw material for planets. There's no evidence that the star actually has any planets, though. But that's not the case for a star system that appears close to Denebola. More about that system tomorrow.

Script by Damond Benningfield, Copyright 2008

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