NASA’s Kepler mission has confirmed the discovery of six planets orbiting a sun-like star, Kepler-11. This is the largest group of planets outside our solar system found to be orbiting a single star. The Kepler mission is also NASA's first finding of Earth-sized planets inside the "habitable zone"--an area where liquid water could exist on a planet's surface.
“The historic milestones Kepler makes with each new discovery will determine the course of every exoplanet mission to follow, “said Doug Hudgins, Kepler program scientist at NASA headquarters
Kepler has found 1,235 planet candidates thus far with the new data released on Tuesday. Candidates need follow-up observation and confirmation to ensure they are indeed planets and not large flying debris or asteroids. Out of the 1,235 candidates, 68 are Earth-size; 288 are super-Earth-size; 662 are Neptune-size; 165 are Jupiter-size; and 19 are larger than Jupiter. Of the 54 new planet candidates in the habitable zone, five are near Earth-size with the rest ranging from double the size of Earth to larger than Jupiter.
The Kepler-11 star is roughly 2,000 light years from Earth and is the most tightly packed system of planets discovered so far. All six of the planets have orbits shorter than that of Venus and five of the six have shorter orbits than that of Mercury. The report is based off the observations made from May 12th to September 17th, 2009. The observations covered more than 156,000 stars in Kepler’s view, which amounts to only 1/400th of the sky.
“The fact that we’ve found so many planet candidates in such a tiny fraction of the sky suggests there are countless planets orbiting sun-like stars in our galaxy,“ said William Borucki, the mission’s science principal investigator of NASA’s Ames Research Center in Moffett Field, CA. “We went from zero to 68 Earth-sized planet candidates and zero to 54 candidates in the habitable zone, some of which could have moons with liquid water.”
Kepler is a space telescope that looks for planets by measuring the brightness of stars and when it decreases it is caused by planets crossing in front of them. This is called transit and since the transits of planets orbiting a sun-like star take about a year to occur, it usually takes three years to locate and verify Earth-sized planets because it requires three transits for verification.