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March 11, 2010

The Sun is a single star. But many stars are double -- they consist of two stars that orbit each other. One of the most beautiful double stars is in Leo, the lion, a constellation that's prominent during spring. And astronomers have found evidence that this beautiful double star has something more: a giant planet.

The star system is Algieba, and it's easy to see, because it's as bright as the North Star. Algieba is in Leo's mane, north of the constellation's brightest star, Regulus.

A telescope shows that Algieba is really two stars that shine a lovely golden yellow. Both stars are giants -- they're much bigger and brighter than the Sun. The stars are farther apart than Pluto is from Earth, so there's plenty of room for planets around each star.

Last year, a team led by astronomers in Korea reported a likely planet orbiting the brighter star in the system. The planet is at least nine times as massive as Jupiter, the largest planet in our own solar system. But the new planet's orbit resembles Earth's: The planet is about 20 percent farther from its star than Earth is from the Sun, and it takes about 14 months to complete an orbit. Because its sun is so much brighter than ours, though, this planet must be much hotter than Earth -- probably too hot to support life.

Still, Algieba's planet shows that planets can exist around double stars -- just as they do around single stars like the Sun.

Tomorrow: a celestial journey.

Script by Ken Croswell, Copyright 2010

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