Scientists see potential for 'another Earth' among 3 newly discovered exoplanets

NASA's Kepler Space Telescope has recently discovered a star with three planets only slightly larger than Earth that can help study the atmosphere of the earth-size worlds, which may provide proof of potential alien life.

The outermost planet orbits in the "Goldilocks" zone, a region where surface temperatures could be moderate enough for liquid water and perhaps life, to exist.

The star, EPIC 201367065, was a cool red M-dwarf about half the size and mass of our own sun. At a distance of 150 light years, the star ranks among the top 10 nearest stars known to have transiting planets. The star's proximity means it's bright enough for astronomers to study the planets' atmospheres to determine whether they are like Earth's atmosphere and possibly conducive to life.

The three planets are 2.1, 1.7 and 1.5 times the size of Earth. The smallest and outermost planet, at 1.5 Earth radii, orbits far enough from its host star that it receives levels of light from its star similar to those received by Earth from the sun, said UC Berkeley graduate student Erik Petigura.

University of Hawaii astronomer Andrew Howard noted that extrasolar planets are discovered by the hundreds these days, though many astronomers are left wondering if any of the newfound worlds are really like Earth. The newly discovered planetary system will help resolve this question.

The new discovery paves the way for studies of the atmosphere of a warm planet nearly the size of Earth. The three new planets are particularly favorable for atmospheric studies because they orbit a nearby, bright star.

Next, the team of astronomers that made the discovery hopes to observe the planets with the Hubble Space Telescope and other observatories to determine what elements are in the planets' atmospheres. If Hubble finds that these warm, nearly Earth-size planets have thick, hydrogen-rich atmospheres, they would learn that there was not much chance for life.

The study is published in the Astrophysical Journal.