Astronomers find most Earth-like planets yet

NEW YORK: Astronomers working with NASA's Kepler planet-finding spacecraft said on Thursday that they had found the most Earth-like worlds yet known in the outer cosmos, a pair of planets that appear capable of supporting life and that orbit a star 1,200 light-years from here in the constellation Lyra.

The newly discovered planets are the two outermost of five worlds circling a yellowish star slightly smaller and dimmer than our Sun, heretofore anonymous and now destined to be known forever in the cosmic history books as Kepler 62. These planets are roughly half again as large as the Earth and are presumably balls of rock, perhaps covered by oceans with humid cloudy skies, although that is at best a highly educated guess.

Nobody will probably ever know if anything lives on these planets, and the odds are that humans will travel there only in their faster-than-light dreams, but the news has sent astronomers intoheavenly raptures. William Borucki of NASA's Ames Research Center, head of the Kepler project, described one the new worlds as the best site for Life Out There yet found in Kepler's four-years-and-counting search for other Earths in the stars. He treated his team to pizza and beer on his own dime to celebrate the find (this being the age of sequestration). "It's a big deal," he said.

Looming brightly in each other's skies, the two planets circle their star at distances of 37 million and 65 million miles, about as far apart as Mercury and Venus in our own solar system. Most significantly, their orbits place them both in the "Goldilocks" zone of lukewarm temperatures suitable for liquid water, the crucial ingredient for Life as We Know It.

Goldilocks would be so jealous.
Previous claims of Goldilocks planets with "just so" orbits snuggled up to red dwarf stars much dimmer and cooler than the Sun have been beset by uncertainties in the size and mass and even the existence of these worlds, said David Charbonneau of the Harvard-Smithsonian Center for Astrophysics, an exoplanet hunter and member of the Kepler team.

"This is the first planet that ticks both boxes," Dr Charbonneau said, speaking of the outermost planet, known as Kepler 62f. "It's the right size and the right temperature." Kepler 62f is 40 percent bigger than Earth and smack in the middle of the habitable zone, with a 267-day year. In an interview, Mr Borucki called it the best planet Kepler has found

Its mate, known as Kepler 62e, is slightly larger — 60 percent bigger than Earth — and has a 122-day orbit, placing it on the inner edge of the Goldilocks zone. It is warmer but also probably habitable, astronomers said.

The Kepler 62 system resembles our own solar system, which also has two habitable planets: Earth and Mars, which once had water and would still be habitable today if it were more massive and had been able to hang onto its primordial atmosphere.

The Kepler 62 planets continue a string of breakthroughs in the last two decades in which astronomers have gone from detecting the first known planets belonging to other stars, or exoplanets, broiling globs of gas bigger than Jupiter, to being able to discern smaller and smaller more moderate orbs — iceballs like Neptune and, now, bodies only a few times the mass of Earth, known technically as super-Earths.

Kepler 62's newfound worlds are not still not quite small enough to be considered strict replicas of Earth, but the new results have strengthened the already rabid conviction among astronomers that the galaxy is littered with billions of Earth-size planets, perhaps as many as one per star, and that astronomers will soon find Earth 2.0, as they call it — our lost twin bathing in the rays of an alien sun.

"Kepler and other experiments are finding planets that remind us more and more of home," said Geoffrey Marcy, a veteran exoplanet hunter at the University of California, Berkeley, and Kepler team member. "It's an amazing moment in science. We haven't found Earth 2.0 yet, but we can taste it, smell it, right there on our technological fingertips."