Edmonds astronomer discovers most earth-like planet yet

Apr 25, 2013
Eric Agol

A University of Washington astronomer from Edmonds has made a huge discovery in the science world. So huge, in fact, that last week it was the top story in Google News’s Science Division.

Eric Agol has identified a small, probably rocky, planet that orbits a sun-like star in the Lyra constellation, 1,200 light years away.

The planet has been named “Kepler 62f,” and scientists believe it is “perhaps the most earthlike planet yet found outside the solar system by the Kepler Space Telescope.”

The Kepler telescope is a space observatory orbiting nearly 93 million miles above Earth.

Kepler 62f is just under 1½ times the size of Earth; it receives half the radiation and circles its star in 267 days.

Agol explains the significance of his find:

“It's not the first planet found in the habitable zone,” he said, “but there were three new planets that were announced in the habitable zone, all of which were smaller (in terms of diameter) than other planets found before.

“The one I found was the smallest, and thus most similar to Earth, only about 40 percent bigger than Earth in diameter.”

The star it orbits is called Kepler 62, and its habitable zone is the space that could be the right distance to planets to allow the presence of water.

"The planets this small that we have found until now have been very close to their stars and much too hot to be possibly habitable,” Agol said. “This is the first one Kepler has found in the habitable zone that satisfies this small size.

"Kepler 62f is the smallest size and the most promising distance from its star, which by these measures makes it the most similar planet to Earth that has been found by Kepler."

Agol says his best guess is that the planet is rocky and has some atmosphere.

The discovery was published in the April 18 edition of Science Express, the online edition of the journal Science.

A number of scientists had been ready to publish their findings on Kepler 62 and its planets when Agol contacted them and informed them he had found another planet orbiting the star.

Agol developed a process that takes into account the slight variation of stellar brightness in the vicinity of a “transit” that causes their host stars to appear fainter when the planets pass in front as they orbit.

He said, “Kepler takes digital images of the sky every six seconds, then adds them up over 30 minutes and sends back a portion of those pictures (cutouts, or 'postage stamps' around 150,000 stars).

“Then, these are summed up to plot the total amount of light (literally photons) received from each star over a 30-minute period,” he said.

“If this shows a drop over a few hours that repeats every orbital period (at least three times for confirmation), then we know that a planet has passed in front of the star causing it to dim.”

Although the mass and density of the planet are not yet known, Agol has also pioneered a process called transit timing, variations that may show the mass of planets by the gravitational effect they have on each other.

"This type of discovery is the reason we launched the Kepler spacecraft — to find small, Earth-sized, potentially Earth-temperature planets," he said. "At the same time, though, it isn't exactly the same as Earth. It is slightly larger and cooler than Earth.

“It tells me how special the Earth is and how it may take some time — hopefully not too long — to find its exact twin.”

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