Meet Earth 2.0: Nasa finds new planet just like ours
A planet remarkably similar to Earth and potentially capable of sustaining life has been discovered in a "habitable zone" around a distant sun-like star.
The planet, which is about 60pc bigger than Earth, is located about 1,400 light years away in the constellation Cygnus.
It was discovered using Nasa's Kepler space telescope and circles a star that is similar in size and temperature to the sun.
"In my mind, this is the closest thing we have to another planet like the Earth," said astronomer Jon Jenkins, with the US space agency's Ames Research Center in Moffett Field, California.
This is "the closest twin, so to speak, to Earth 2.0", said John Grunsfeld, Nasa's science mission chief. "This is about the closest so far and I really emphasise the 'so far'."
Dubbed Kepler-452b, the planet is positioned about as far from its parent star as Earth is from the sun. At that distance, surface temperatures would be suitable for liquid water, a condition believed to be critical for life.
Scientists previously have found Earth-sized planets orbiting in stars' so-called "habitable zones", but those stars are cooler and smaller than the sun.
Nasa launched the Kepler telescope in 2009 to survey a sampling of nearby stars in an attempt to learn if planets like Earth were common in the galaxy.
"This is great progress in finding a planet like Earth that is similar in size and temperature around a sun-like star," said Kepler scientist Jeff Coughlin, with the SETI Institute in Mountain View, California.
Based on its size, scientists believe Kepler-452b should be rocky, like the Earth, though that theory is based on statistical analysis and computer modelling, not direct evidence.
One unanswered question is whether the planet is rocky. Scientists believe there's a better than even chance it is.
Kepler-452b's parent star is about 6 billion years old, compared to the 4.6 billion year age of the sun.
"It's simply awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star," Mr Jenkins said.
"That's considerable time and opportunity for life to arise somewhere on its surface or in its oceans should all the necessary ingredients and conditions for life exist on this planet," he added.
With the discovery of Kepler-452b, the telescope has found 1,030 confirmed planets and identified nearly 5,000 candidate planets. The list of potential planets includes 11 other near-Earth twins, seven of which circle sun-like stars.
Attempts to learn if Kepler-452b has an atmosphere likely will have to wait for a new generation of more sensitive space telescopes, said Nasa's associate administrator John Grunsfeld.
Planet 452b takes 385 days to orbit its star, just a little more than Earth takes for a one-year lap. It's just a bit farther from its star than Earth is from our sun.
The planet is in a solar system that is 1,400 light years from our own, located in the Constellation Cygnus, or swan.
"So pack your bags, it's a long trip," joked Jenkins.
Altogether, the catalogue now includes 4,661 exoplanet candidates. Slightly more than 1,000 of them are confirmed to be planets.
The research will be published in 'The Astronomical Journal'.