NASA milestone: We're one step closer to 'finding Earth's twin'

Scientists are one step closer to finding a new Earth. NASA's Kepler mission has discovered its first planet located within the "habitable zone." That means its surface can hold liquid water, i.e., it could sustain life!

NASA's calling the new planet Kepler-22b. It's located 600 light-years away, and it's about 2.4 times the radius of Earth. At the moment, scientists are still unsure about the planet's composition. Yes, it can hold water, but there's no confirmation about its surface being rocky, gaseous or even liquid. Despite the unknown, they believe finding Kepler-22b is a step in the right direction.

Kepler program scientist Douglas Hudgins said, "This is a major milestone on the road to finding Earth's twin. Kepler's results continue to demonstrate the importance of NASA's science missions, which aim to answer some of the biggest questions about our place in the universe."

Speaking of Earth's twin, Kepler-22b does share some notable similarities. It orbits a sun-like star in about 290 days, with its host star belonging to the same class as our sun, which is called G-type. Of the 54 habitable zone planet candidates reported in early February, Kepler-22b is the first to be confirmed.

So how does Kepler find these habitable planets? They measure dips in the brightness of more than 150,000 stars to search for planets that cross in front of, or "transit," them. The program needs at least three transits to confirm a signal as a planet.

More info on Kepler-22b will be published in The Astrophysical Journal.

(via NASA)

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