NASA discovers two Earth-size planets outside Solar system

Houston, Dec 21: An Earth-size planet orbiting a Sun-like star outside the Solar system has been discovered by NASA's Kepler mission, in what is being described as an encouraging sign for prospects of finding life elsewhere.

The planets, named Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet's surface, but they are the smallest exoplanets ever confirmed around a star like Sun.

This major milestone, one of its first, suggests that far from being rare, our galaxy is filled with planets that may look a lot like our pale blue dot.

One of the two new planets, Kepler-20f, has a diameter that's 3 per cent larger than Earth's. The second planet, Kepler-20e, has a diameter that's 15 per cent smaller than Earth's.

"We've crossed a threshold: This is the first time we've crossed the Earth-size threshold," said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass, who led the study.

The discovery, published in the journal Nature, brings scientists tantalizingly close to finding the holy grail of planet hunters: an Earth-like world in a habitable zone.

These planets, while roughly the size of our planet Earth, are circling very close to their star, giving them fiery temperatures that are most likely too hot to support life, researchers said.

The discovery, however, brings scientists one step closer to finding a true twin of Earth that may be habitable.

PTI