NASA Discovers New Solar System with 6 Planets
 NASA's Kepler space telescope spots odd new solar system with five planets orbiting close to a distant star. Jane Ross reports.
This is the largest group of transiting planets orbiting a single star yet discovered outside our solar system," NASA said.

With temperatures hotter than Venus -- likely more than 400 to 1,400 degrees Fahrenheit, the six planets range in size from twice to four and a half times Earth’s diameter, astronomers said.

The five confirmed planets are larger in mass but less dense than Earth, and closely packed, taking from 10 to 47 days to orbit the star. Astonomers said there is almost certainly a sixth planet orbiting nearly twice as far away, but its distance from the star makes its confirmation more difficult.

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According to NASA, all of the planets orbiting Kepler-11 are larger than Earth, with the largest ones being comparable in size to Uranus and Neptune. The innermost planet, Kepler-11b, is ten times closer to its star than Earth is to the sun. Moving outward, the other planets are Kepler-11c, Kepler-11d, Kepler-11e, Kepler-11f, and the outermost planet, Kepler-11g, which is half as far from its star as Earth is from the sun.

The planets Kepler-11d, Kepler-11e and Kepler-11f have a significant amount of light gas, which indicates that they formed within a few million years of the system's formation, NASA said.

These six planets, which are mixtures of rock and gases possibly including water, were found by tracking the dimming of a star’s light when planets pass between the star and the telescope, astronomers said.

The astronomers said the next step will be to determine mass and orbits of the planets more precisely, providing clues to how the planets formed.

"Much of the scientific community thought that multiple planets transiting the same star would be unlikely," said Eric Ford of NASA team and University of Florida associate professor. "That idea has been completely overturned by this new discovery. Without the transit-timing method, these planets might have gone unconfirmed for years."

The discoveries are part of several hundred new planet candidates identified in new Kepler mission science data, released on Tuesday. The findings increase the number of planet candidates identified by Kepler to-date to 1,235.