Scientists find closest thing yet to Earth-sun twin system

CAPE CANAVERAL, Fla. - Scientists have identified a "close cousin" to Earth that is orbiting a sunlike star and that resembles Earth more than any of the 1,000 other planets so far discovered outside the solar system.

"It is the closest thing that we have to another place that somebody else might call home," said Jon Jenkins from NASA's Ames Research Center in California.

The researchers announced their discovery Thursday based on observations from NASA's Kepler space telescope.

The planet is in a solar system 1,400 light-years from our own, in the constellation Cygnus, or swan.

This older, bigger cousin to Earth is called Kepler-452b. What makes this planet remarkable is that it orbits its star at about the same distance that Earth orbits the sun. What's more, its home star looks to be similar to our sun. Jenkins noted it's the nearest thing yet to another Earth-sun twin system.

"Today the Earth is a little less lonely because there's a new kid on the block," said Jenkins, who led the team that discovered Kepler-452b.

The last Kepler discovery that had scientists gushing was just over a year ago. That close-to-Earth-size planet, Kepler-186f, also was in the habitable zone of its star. But that faint dwarf star was unlike our sun.

John Grunsfeld, NASA's science mission chief, emphasized that the exoplanet system identified Thursday - "a pretty good close cousin to the Earth and our sun" - was the closest so far. "And I really emphasize the so far."

The planet-hunting Kepler will keep churning out new discoveries, Grunsfeld said, and possibly find even better matches for "Earth 2.0."

Kepler was launched in 2009 and has nearly 5,000 potential exoplanets to its credit, including 1,030 planets - worlds beyond our solar system. It is helping to address such fundamental questions as where do we come from and where are we headed, and arguably the biggest question of all: Are we alone?

Grunsfeld said that thanks to Kepler's latest finding, we're taking "one small step in answering that question today."

While scientists are uncertain whether Planet 452b is rocky like Earth, they believe there's a better-than-even chance it is.

As for the age and size, it is about 6 billion years old, 1.5 billion years older than Earth, and 60 percent larger in diameter than our home planet. Its star, Kepler 452, is also older and bigger, as well as brighter than our sun.

Planet 452b takes 385 days to orbit its star, just a little more than Earth takes. It's just a bit farther from its star than Earth is from our sun. That's important because it makes the planet ripe, potentially, for liquid water on the surface.

But scientists can't say for sure just how much like Earth this strange new world really is. The Kepler isn't getting a close-up view - it's measuring the newly found planets based on the way they dim the light of their host stars as they pass in front of them.