Earth, with its majestic oceans, life-sustaining atmosphere, and perfectly temperate climate, seems like a pretty special place. But new data gathered by NASA's planet-scouting Kepler telescope shows that the world we call home isn't quite so one-of-a-kind after all.
Astronomers now estimate that there may be as many as 40 billion potentially habitable Earth-like planets out there. And — better yet — the closest one is only 12 light-years away.
The calculations were performed by Erik Petigura, a graduate student at UC Berkeley. That 40 billion figure means that "one out of every five sun-like stars in the galaxy has a planet the size of Earth circling it," in what astronomers affectionately term the "Goldilocks zone," according to the New York Times. Kepler's primary duty is spotlighting planets that fall within these "just right" parameters.
The Goldilocks zone, as the name suggests, fulfills a basic set of conditions that make a planet theoretically habitable. Planets sitting inside it can't be too hot, or too cold; too big, or too small; too close to their respective "sun," or too distant. They have to be just right. These requirements are what make Earth, well, Earth.
How the Kepler telescope, which is in permanent orbit around the sun, spots new planets isn't all that complicated. Essentially, it identifies space objects that "transit" as they pass in front of distant stars, like a speck of dust in morning light. The star dims accordingly, depending on the object's size and relative distance to Kepler's lens.
Since its launch in 2009, the planet-hunting spacecraft has confirmed the existence of more than 3,500 exoplanets — and the number continues to climb, delighting astronomers. "When I first started working with Kepler right before launch, I thought there would be maybe a thousand planets that Kepler would find," said Jason Rowe, an astronomer at the Search for Extraterrestrial Intelligence Institute in Mountain View, Calif., during a press conference.
The latest findings also suggest a sobering new paradigm in which our beautiful blue marble might not be quite so special after all. "When you look up at the stars in the night sky, how many of them have a planet like the Earth?" Petigura asked the Washington Post.
The answer, apparently, is plenty.
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