for National Geographic News
The find may increase the chances of finding life-supporting "exoplanets," they added.
The planet, dubbed MOA-2007-BLG-192Lb, is just three times more massive than Earth and orbits what is most likely a brown dwarf—a "failed" star that is so small its core may not be massive enough to maintain nuclear reactions for very long.
The planet is 3,000 light-years from Earth and has a close-in orbit similar to Venus's. But because the newfound body's parent is so much cooler than our sun, MOA-2007-BLG-192Lb is most likely to be even colder than Pluto.
Even so—and despite almost no solar heating—there's a slim chance that the planet could maintain a habitable temperature if the atmosphere is as thick with molecular hydrogen as researchers think it could be, according to study leader David Bennett.
The record-breaking planet—the only smaller one has been found orbiting a pulsar, a rapidly spinning neutron star—was announced Monday at an American Astronomical Society meeting in St. Louis, Missouri.
(Related: "Mysterious 'Super Earth' Is Smallest Known Exoplanet?" [April 11, 2008].)
Bennett said the discovery is a shot in the arm for the search for habitable planets outside our solar system.
"The fact that we're finding outer planets around low-mass objects is an indication that planets are forming in these low-mass systems," the University of Notre Dame physicist said.
Many such systems are relatively nearby and would be easy places to take the next step—the search for life.
Brown or Red?
MOA-2007-BLG-192 is the seventh exoplanet to be discovered using a technique called gravitational microlensing. But it's the first for which researchers didn't have to rely on follow-up observations to confirm the planet's presence.
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