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March 6, 2010

If you have a compass, let it point you to the southeast as night falls for the constellation Pyxis -- the celestial compass. It's a short streak of faint stars, aiming toward the remnants of the Argo -- the ship that carried Jason and the Argonauts. In fact, Pyxis represents the Argo's compass.

You need a pretty dark sky to see even its brightest star. But that's only because the star is more than 800 light-years away. If you moved it to the distance of Sirius, the brightest star in the night sky, Alpha Pyxidis would outshine everything except the Sun and Moon.

In astronomical parlance, Alpha Pyx is class B. Astronomers classify stars by their surface temperature and color -- hot stars are blue, while cool stars are orange or red. The hottest stars are class O, followed by class B. Alpha Pyx is tens of thousands of degrees hotter than the Sun, so it shines blue-white.

The star is so hot because it's more than 10 times as massive as the Sun. Gravity squeezes the star tightly, making its interior intensely hot.

As a result of the high temperatures in its core, Alpha Pyx is "burning" its hydrogen fuel in a hurry. So even though the star is less than one percent the age of the Sun, it's already nearing the end of its life. Within a few million years, the star may go out with a titanic explosion known as a supernova.

A different kind of star in Pyxis seems headed for the same fate -- and we'll talk about that tomorrow.

Script by Damond Benningfield, Copyright 2010

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