NASA makes out-of-this-world discovery

(NBC) - NASA officials are excited about the discovery of the first confirmed planetary system with more than one planet transiting the same star.

A NASA animation shows the sun-like star, called "Kepler Nine," and the new planets, called "Kepler 9B" and "Kepler 9C."

The discovery is based on seven months of observations of more than 156,000 stars.

Investigators were looking for subtle brightness changes as part of an ongoing search for earth-sized planets outside the solar system.

One NASA official said these planets are three- or four times larger than Earth, and timing their orbits made the discovery possible.

"The discovery is especially important because this transit timing method allows us to confirm even smaller planets exist," said William Borucki, Kepler principal investigator. "We ought to be able to confirm even Earth-sized planets exist, so that's extremely important."

And Borucki said the planets are hot.

"They have orbital periods of 19 days and 38 days, well inside the orbit of Earth or Mercury, in fact. So they're very hot, and they're certainly gas planets."