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Zeta Puppis

February 20, 2010

By everyday standards, the surface of the Sun is pretty darned hot -- more than 10,000 degrees Fahrenheit. By stellar standards, though, the Sun is just lukewarm. Other stars surpass it by many thousands of degrees.

One of the hottest is Zeta Puppis, the brightest star of the constellation Puppis. It's due south around 10 p.m., well to the lower left of brilliant Sirius and not far above the southern horizon.

Astronomers classify stars based on their surface temperature. Zeta Pup is a member of the hottest class -- class "O." These stars are much more massive than the Sun, so they burn through their nuclear fuel at a furious rate, producing enormous amounts of energy. This heats their surfaces to blue-hot incandescence.

Even among O stars, though, Zeta Pup is a scorcher -- about 75,000 degrees. At such an extreme temperature, it emits most of its energy in the ultraviolet -- wavelengths that are invisible to human eyes, but that produce sunburn and other unpleasant effects. And there's a lot of it: When you add up the ultraviolet, visible light, and all other wavelengths, Zeta Pup shines about 350,000 times brighter than the Sun.

Any planets that were born close to Zeta Pup wouldn't have lasted long -- they would have been vaporized by the intense radiation. In fact, to have Earth-like conditions, a planet would have to be about 500 times farther from Zeta Pup than Earth is from the Sun. And that's hot by any standard.

Script by Damond Benningfield, Copyright 2009

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