Planet hunters say it's just a matter of time before they lasso Earth's twin, which almost surely is hiding somewhere in our star-studded galaxy.
Momentum is building: Just last week, astronomers announced they had discovered three super-Earths -- worlds more massive than ours but small enough to most likely be rocky -- orbiting a single star. And dozens of other worlds suspected of having masses in that same range were found around other stars.
"Being able to find three Earth-mass planets around a single star really makes the point that not only may many stars have one Earth, but they may very well have a couple of Earths," said Alan Boss, a planet formation theorist at the Carnegie Institution of Washington in Washington, D.C.
Since the early 1990s, when the first planets outside of our solar system were detected orbiting the pulsar PSR 1257, astronomers have identified nearly 300 such worlds. However, most of them are gas giants called hot Jupiters that orbit close to their stars because, simply, they are easier to find.
"So far we've found Jupiters and Saturns, and now our technology is becoming good enough to detect planets smaller, more like the size of Uranus and Neptune, and even smaller," said one of the top planet hunters on this world, Geoff Marcy of the University of California, Berkeley.
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