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An artist’s depiction of Kepler-62f, a newly discovered planet in the “habitable zone.” (NASA image.)

They’re in the zone.

The habitable zone, that is: In a paper published today in Science, a team of astronomers announced that they’ve identified two planets orbiting a star not too unlike our own in a system in the Lyra constellation, 1,200 light years away. What makes their discovery special is the size of the two planets.

(Photo courtesy of the Planetery Habitability Laboratory)
Eric Agol, a UW astronomer, has worked with a team of scientists to find Kepler 62f, the smallest, most “earthlike” exoplanet yet discovered.

One is Kepler-62f, named after the Kepler Space Telescope that helped astronomers find these new worlds. It moves around its star in 267 days.

“It’s about 40 percent bigger than Earth, which is the smallest that’s been found in the so-called habitable zone,” said Eric Agol, a University of Washington associate professor of astronomy and the second author of the Science paper — a designation that recognizes his role in discovering Kepler-62f.

Working with the space telescope’s software, Agol was able to tease out the presence of the two new planets with help from Brian Lee, a UW postdoctoral researcher. That process — based on the tiniest dips in brightness in the light emitted by a star encircled by its planets — may lead to similar discoveries down the line, said Agol.

Eric Agol
Eric Agol, University of Washington astronomer.

Lee and Agol’s next steps will include “trying to automate [this method] and make it a little more robust,” he said.

The second planet, Kepler-62e, is 1.61 times as big as Earth, and orbits its star in 122 days. The three other planets already found in the same system are smaller or bigger than Earth, but not in that sweet spot where the temperature is ideal for life (as we know it).

Jake Vanderplas, another UW postdoctoral researcher and astronomer, said today’s news marked a crucial step toward finding planets like our own.

“The reason why people are interested in planets is because they’re interested in other beings out there,” he said.

One goal is to to give future instruments (including space-based telescope arrays) a better set of targets to choose from.

So far we’ve noted their presence by their absence, or by their shadows as they cross their stars, Vanderplas said. The amount of light from these stars blocks out any direct images of the planets, and keeps us from directly observing the photons that come from them. If and when we do, we can deduce more about their chemical composition.

If you see oxygen, for example, in a planet’s photons (and presumably from its atmosphere), that could be a tantalizing hint that there are biological processes at work.

That would certainly “spur more thinking about how to look at that up close,” Vanderplas said. Within our lifetimes, depending on funding, we could see the discovery of a truly “earthlike” (i.e. one bearing water) exoplanets.

In the meantime, just the presence of these planets is encouraging, he said. “We’ll be able to plug more certain numbers into the Drake equation when we try to figure out how many lifeforms are out there.”

Will Mari is a phd candidate in the UW Dept. of Communication. He studies media history and the history of tech. He also tweets about etymology @willthewordguy.

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