JPL: Planet Shares Similarities With Earth

Like the most selective Ivy League admissions committees, the NASA Kepler mission has confirmed only 28 planets out of 2,326 planet candidates. Monday, Kepler confirmed its first planet located in a habitable zone, an area around a star where liquid water could potentially exist on a planet's surface. This brings scientists one giant leap closer to finding a planet similar to Earth.

Dubbed Kepler-22b, the planet is about 2.4 times the radius of Earth. Scientists have not yet determined if it is mostly gaseous, liquid or rocky in composition. Sitting 600 light years from Earth, Kepler-22btakes 290 days to orbit its star, which is close in similarity to our sun. In Febrruary, the Kepler mission reported 54 habitable zone planet candidates. Kepler-22b is the first to be confirmed.

"This is a major milestone on the road to finding Earth's twin," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington, in a press release from .  "Kepler's results continue to demonstrate the importance of NASA's science missions, which aim to answer some of the
biggest questions about our place in the universe."

Kepler mission scientists pay close attention to the brightness of stars, measuring drops in brightness that could signal a planet moving in orbit around the star. The team must observe at least three such dips in brightness to consider a planet candidate exists in that orbit. The Spitzer Space Telesope as well as ground-based telescopes are used to focus in and observe planet candidates. Currenlty, more than 150,000 stars are being observed.

Currently, the Kepler team is hosting its inaugural conference at the NASA Ames Research Center, where it is announcing the findings of observations conducted from May 2009 to September 2010. Since its last catalog put together in February, Kepler had increased the number of identified planet candidates 89 percent to 2,326, of which 207 are approximately the same size as Earth. The number of these Earth-sisedd planets has increased more than 200 percent since February.

"The tremendous growth in the number of Earth-size candidates tells us that we're honing in on the planets Kepler was designed to detect: those that are not only Earth-size, but also are potentially habitable," said Natalie Batalha, Kepler deputy science team lead in a press release. "The more data we collect, the keener our eye for finding the smallest planets out at longer orbital periods."
 
JPL managed mission development for Kepler. To learn more about Kepler and the planet candidates, visit NASA's Kepler webpage.