February 9, 2011 — Scientists using NASA's Kepler space telescope recently discovered six planets made of a mix of rock and gases orbiting a single sun-like star, known as Kepler-11. This is the largest group of transiting planets orbiting a single star yet discovered outside our solar system.
"The Kepler-11 planetary system is amazing," said Jack Lissauer, a planetary scientist and a Kepler science team member at NASA's Ames Research Center. "It’s amazingly compact, it’s amazingly flat, there’s an amazingly large number of big planets orbiting close to their star - we didn’t know such systems could even exist."
In addition, NASA's Kepler mission has discovered its first Earth-size planet candidates and its first candidates in the habitable zone, a region where liquid water could exist on a planet's surface. Five of the potential planets are near Earth-size and orbit in the habitable zone of smaller, cooler stars than our sun. Candidates require follow-up observations to verify they are actual planets.
"In one generation we have gone from extraterrestrial planets being a mainstay of science fiction, to the present, where Kepler has helped turn science fiction into today's reality," said NASA Administrator Charles Bolden.
The discoveries are part of several hundred new planet candidates identified in new Kepler mission science data, released February 1. The findings increase the number of planet candidates identified by Kepler to-date to 1,235.
The findings are based on the results of observations conducted May 12 to September 17, 2009, of more than 156,000 stars in Kepler's field of view, which covers approximately 1/400 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 of Ames Research Center. "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 looks for planet signatures by measuring tiny decreases in the brightness of stars caused by planets crossing in front of them. This is known as a transit. Since transits of planets in the habitable zone of sun-like stars occur about once a year and require three transits for verification, it is expected to take three years.
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Kepler-11 is a sun-like star around which six planets orbit. At times, two or more planets pass in front of the star at once, as shown in this artist's conception of a simultaneous transit of three planets observed by NASA's Kepler spacecraft on Aug. 26, 2010. Credit: NASA/Tim Pyle
This artist’s conception shows the Kepler-11 planetary system and our solar system from a tilted perspective to demonstrate that the orbits of each lie on similar planes.
Image credit: NASA/Tim Pyle
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