ROUGH CUT - NO REPORTER NARRATION<br/> Scientists have discovered a planet which may be similar to Earth, circling a star 600 light years away.<br/> NASA's findings, the first detection of a potentially habitable world orbiting a Sun-like star, are due to be published in The Astrophysical journal.<br/> It is a key finding in an ongoing quest to learn if life exists beyond Earth.<br/> The planet, called Kepler-22b, is about 2.4 times the size of Earth.<br/> Among 500 planets found to orbit stars beyond our solar system, it is the smallest and the best positioned to have liquid water on its surface -- among the ingredients necessary for habitation.<br/> A light year is the distance light travels in a year, about 6 trillion miles (10 trillion km).
