Astronomers have discovered what they say is the most Earth-like planet yet detected - a distant, rocky world that's similar in size to our planet and exists in the Goldilocks zone where it's not too hot and not too cold for life.
The find, announced on Thursday, excited planet hunters who have been scouring the galaxy for years for potentially habitable spots outside our solar system.
The exoplanet orbits at the outer edge of the habitable temperature zone around its star, the sweet spot where lakes, rivers or oceans may exist without freezing solid or boiling away.
The planet is "the right size and is at the right distance to have properties that are similar to our home planet," said Elisa Quintana of the SETI Institute at NASA's Ames Research Center in California, the lead author of the paper published in the journal Science on Friday.
"We can now say that other potentially habitable worlds, similar in size to Earth, can exist. It's no longer in the realm of science fiction," she told a press conference.
The planet is about 10 percent larger than Earth. Planets 1.5 times the size of Earth or larger, seem to attract a thick hydrogen and helium layer that makes them resemble gas giants like Jupiter or Saturn.
The planet was detected by NASA's orbiting Kepler telescope, which examines the heavens for subtle changes in brightness that indicate that an orbiting planet is crossing in front of a star. From those changes, scientists can calculate a planet's size and make certain inferences about its makeup.
The newfound object, dubbed Kepler-186f, circles a red dwarf star 500 light-years from Earth in the constellation Cygnus.
Quintana said she considers the planet to be more of an “Earth cousin” than a twin because it circles a star that is smaller and dimmer than our sun. While Earth revolves around the sun in 365 days, this planet completes an orbit of its star every 130 days.
“You have a birthday every 130 days on this planet,” she said.
The planet probably basks in an orange-red glow from its star and is most likely cooler than Earth, with an average temperature slightly above freezing, “similar to dawn or dusk on a spring day,” University of California, Berkeley astronomer Geoff Marcy, who had no role in the discovery, told The Associated Press in an email.
Scientists cannot say for certain whether it has an atmosphere, but if it does, it probably contains a lot of carbon dioxide.
However, because dwarf stars are cooler, smaller and dimmer than our sun, they interact differently with planets, researchers said.
"It is also slightly larger than the Earth, and so the hope would be that this would result in a thicker atmosphere that would provide extra insulation," explained San Francisco State University astronomer Stephen Kane, another member of the team behind the discovery.
"Some people call these habitable planets, which of course we have no idea if they are," said Kane. "We simply know that they are in the habitable zone, and that is the best place to start looking for habitable planets."
Since its launch in 2009, Kepler has confirmed 961 planets, but only a few dozen are in the habitable zone. Most are giant gas balls, and not ideal places for life. Scientists in recent years have also found planets slightly larger than Earth in the Goldilocks zone called “super Earths,” but it is unclear if they are rocky.
(FRANCE 24 with AP, REUTERS)
Date created : 2014-04-18