Astronomers with NASA's Kepler mission have confirmed the existence of an Earth-like planet in a “habitable zone” outside our solar system.
The new planet, Kepler-22b, was discovered by NASA’s Kepler space telescope, which sifts through the universe in search for Earth like planets.
While Kepler has found more than 2,000 possible planets, a potentially habitable planet with an environment quite similar to that of Earth and best positioned to have water and even life has proved elusive -- until now.
Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington, said, “This is major milestone on the road to finding Earth's twin. Kepler's results continue to demonstrate the importance of Nasa's science missions, which aim to answer some of the biggest questions about our place in the universe.”
Kepler 22-b was marked as a “candidate” planet shortly after NASA launched its Kepler spacecraft in March 2009. However, Kepler 22b needed three transits around its star to confirm the initial observation.
Kepler-22b shares some key aspects with Earth. Roughly 2.4 times the size of Earth, the new planet is some 600 light years away, which places it squarely in the so-called “Goldilocks zone,” where liquid water could exist on the surface.
Kepler-22b spins around a G-type star, a lot like our very own sun, and follows a 290 day orbit.
The planet is about 15 percent nearer to its star, which is cooler (by about 220 degrees), a bit dimmer and smaller than Earth’s sun.
Preliminary estimates indicate that its surface temperature is about 72 degrees Fahrenheit (22 Celsius), making it relatively pleasant from human perspective.
From the early observations, Kepler astronomers have been unable to ascertain whether the planet is rocky, gaseous or liquid.
“I think there are two things that are really exciting about Kepler-22b. One is that it's right in the middle of this habitable zone,” Natalie Batalha, Kepler deputy science team lead at San Jose State University in California, said in a press conference.
“The second thing that's really exciting is it's orbiting a star very, very similar to our own sun. This is a solar analogue, almost a solar twin, very similar to our own sun and you've got a planet 2.4 times the size of the Earth right smack in the habitable zone,” she added.
The Kepler data
Kepler 22-b was marked as a “candidate” planet shortly after NASA launched its Kepler spacecraft in March 2009. However, Kepler 22-b needed three transits around its star to confirm the initial observation.
In June 2010, the Kepler team announced 312 planet candidates over the first four months of the mission. In February 2011, the number rose to 1,235 potential planets orbiting 997 stars. Since then, the Kepler Space Telescope has found 1,094 more planetary candidates increasing the total number to 2,326.
Of these, 207 are approximately Earth-size, 680 are super Earth-size, 1,181 are Neptune-size, 203 are Jupiter-size and 55 are larger than Jupiter.