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Penn State has hand in discovery of most Earth-like planet yet

| Thursday, April 17, 2014, 3:24 p.m.
This artist's rendering provided by NASA on Thursday, April 17, 2014, shows an Earth-sized planet dubbed Kepler-186f orbiting a star 500 light-years from Earth. Astronomers say the planet may hold water on its surface, and is the best candidate yet of a habitable planet in the ongoing search for an Earth twin.

Astronomers have discovered what they say is the most Earth-like planet yet detected — a distant, rocky world that's similar in size and exists in the “Goldilocks” zone where it's not too hot and not too cold.

The team includes Penn State scientists using data from NASA's Kepler Space Telescope, which examines the heavens for subtle changes in brightness that indicate 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.

Researchers have collected data about more than 3,900 possible planets, but of the 961 they've confirmed, all but this newfound object are at least 40 percent larger than Earth, Penn State professor of astronomy and astrophysics Eric Ford said.

Ford, who co-authored a paper in the journal Science announcing the find, said the planet, dubbed Kepler-186f, circles a red dwarf star 500 light years from Earth in the constellation Cygnus. A light year is nearly 6 trillion miles.

The planet is about 10 percent larger than Earth and may have liquid water on its surface, scientists said. Its star is much cooler than Earth's sun and emits most of its radiation as infrared light rather than visible light.

Questions linger about the planet's atmosphere, surface temperature and possible life forms, Ford said.

The planet probably basks in an orange-red glow from its star and is likely cooler than Earth, with an average temperature slightly above freezing, “similar to dawn or dusk on a spring day,” said University of California, Berkeley astronomer Geoff Marcy, who had no role in the discovery.

Lead researcher Elisa Quintana at NASA's Ames Research Center 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 Earth's sun. While Earth revolves around the sun in 365 days, this planet completes an orbit of its star every 130 days.

Kepler-186f is part of a system of five planets, all of which are about Earth's size. The other planets are too close to their star to support life.

The planet is too far away for further exploration, even for next-generation space telescopes.

The Associated Press contributed. Megan Harris is a staff writer for Trib Total Media. Reach her at 412-388-5815 or mharris@tribweb.com.

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