Scientists find Earth-sized world in orbit friendly to life

CAPE CANAVERAL, Florida Thu Apr 17, 2014 3:08pm EDT

Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone?a range of distance from a star where liquid water might pool on the planet's surface, is seen in a NASA artist's concept released April 17, 2014. REUTERS/NASA/JPL-Caltech/Handout

Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone?a range of distance from a star where liquid water might pool on the planet's surface, is seen in a NASA artist's concept released April 17, 2014.

Credit: Reuters/NASA/JPL-Caltech/Handout

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CAPE CANAVERAL, Florida (Reuters) - For the first time, scientists have found an Earth-sized world orbiting in a life-friendly zone around a distant star.

The discovery, announced on Thursday, is the closest scientists have come so far to finding a true Earth twin. The star, known as Kepler-186 and located about 500 light years away in the constellation Cygnus, is smaller and redder than the sun.

The star's outermost planet, designated Kepler-186f, receives about one-third the radiation from its parent star as Earth gets from the sun, meaning that high noon on this world would be roughly akin to Earth an hour before sunset, said astronomer Thomas Barclay, with NASA's Ames Research Center in Moffett Field, California.

The planet is the right distance from its host star for water -- if any exists -- to be liquid on the surface, a condition that scientists suspect is necessary for life.

"This planet is an Earth cousin, not an Earth twin," said Barclay, who is among a team of scientists reporting on the discovery in the journal Science this week.

NASA launched its Kepler space telescope in 2009 to search about 150,000 target stars for signs of any planets passing by, or transiting, relative to the telescope's point of view. Kepler was sidelined by a positioning system failure last year.

Analysis of archived Kepler data continues. From Kepler's observational perch, a planet about the size and location of Earth orbiting a sun-like star would blot out only about 80 to 100 photons out of every million as it transits.

The pattern is repeated every 365 days and at least three transits would be needed to rule out other possibilities, so the search takes time.

"It's very challenging to find Earth analogs," Barclay said. "Most candidates don't pan out, but things change as we get more measurements."

Scientists don't know anything about the atmosphere of Kepler-186f, but it will be a target for future telescopes that can scan for telltale chemicals that may be linked to life.

"This planet is in the habitable zone, but that's doesn't mean it is habitable," Barclay said.

So far, scientists have found nearly 1,800 planets beyond the solar system.

"The past year has seen a lot of progress in the search for Earth-like planets. Kepler-168f is significant because it is the first exoplanet that is the same temperature and is (almost) the same size as Earth," astronomer David Charbonneau, with the Harvard-Smithsonian Center for Astrophysics, wrote in an email.

"For me the impact is to prove that yes, such planets really do exist," Charbonneau said. "Now we can point to a star and say, "There lies an Earth-like planet.'"

(Editing by Leslie Adler)

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Comments (4)
Artimas wrote:
Interesting, good work Science!

Apr 17, 2014 2:50pm EDT  --  Report as abuse
morbas wrote:
Spave Fellowship News indicates a 130day orbital.
http://spacefellowship.com/news/art38180/kepler-186-and-the-solar-system.html

Apr 17, 2014 5:57pm EDT  --  Report as abuse
gregbrew56 wrote:
From the article: “The pattern is repeated every 365 days and at least three transits would be needed to rule out other possibilities, so the search takes time.”

Did the author mean that the ability of the space telescope to observe the Keppler-186 system only happened when the telescope was in a specific location in the *telescope’s* 365-day orbit?

The odds that the indirectly observed planet (Keppler-186f) has a 365 day year are exceedingly low.

Being that the space telescope and the system being observed share the same name (Keppler) could be a source of confusion.

The article could be written a bit more clearly, as the wording seems to imply that Keppler-186f has an orbital period of 365 days.

Thanks for the link, morbas.

Apr 18, 2014 11:03am EDT  --  Report as abuse
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