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Moon and Saturn

November 2, 2010

In our own solar system, the planet Saturn is a giant -- it’s second only to Jupiter. In other star systems, though, Saturn-sized worlds are pretty common -- astronomers have discovered scores of them. In fact, one system has at least two Saturn-sized worlds.

The star is Kepler 9. It’s the ninth star for which the Kepler spacecraft has discovered planets. Kepler is searching for planets around more than 150,000 stars. It looks for planets to cross in front of their stars as seen from Earth, causing the stars’ brightness to dip by a tiny bit.

The goal is to find Earth-sized planets around Sun-like stars. Bu Kepler’s also discovering lots of other planets, including at least two that orbit Kepler 9, which is about the same size, mass, and temperature as the Sun.

Both planets -- Kepler 9a and 9b -- are almost as massive as Saturn. One of them orbits the star once every 19 days, while the other takes about twice as long. The short periods mean that both planets are closer to the star than any of the planets of our solar system are to the Sun. And there’s evidence of a third planet even closer to the star. It’s a good bit smaller than Saturn, though -- most likely a super-heated chunk of rock roasting in the heat of the nearby star.

Our own Saturn is in view in the east-southeast before dawn. It looks like a bright star. And it’s especially easy to pick out tomorrow because it’s just to the lower left of the crescent Moon.


Script by Damond Benningfield, Copyright 2010


Today's program was made possible in part by a grant from NASA.


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