NASA Discovers Earth's 'Older, Bigger Cousin'

NASA's planet-hunting Kepler telescope has spotted an Earth-like world 1,400 light years away, the space agency has announced.

Kepler-452b is 60% larger in diameter than Earth and orbits a sun-like star in the constellation Cygnus, said NASA.

The new world sits squarely in the so-called habitable zone - where life could exist because it is neither too hot nor too cold to support liquid water.

Its mass and composition have not yet been established, but researchers believe there Is a good chance Kepler-452b is made of rock.

It takes 385 days for the planet to orbit its star, says NASA, not far off Earth's 365-day year.

NASA scientist Jon Jenkins said: "We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth's evolving environment.

"It's awe-inspiring to consider that this planet has spent six billion years in the habitable zone of its star; longer than Earth.

"That's substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet."

On Thursday, NASA added 521 new possible planets to the 4,175 already found by the Kepler space telescope.

Twelve of the new planet candidates have diameters between one to two times that of Earth and are in a habitable zone.

Of these, nine orbit stars that are similar to our sun in size and temperature, says NASA.

NASA has found other planets in the habitable zone, but they've been unable to support life because they are either too big or too close to their parent stars.

Kepler launched in 2009 to search for planets outside our solar system, particularly those like Earth.

The telescope watches for dips in the brightness of stars, telltale signs of possible planets passing between the star and the telescope.