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Scientists closing in on Earth-size exoplanets

An international consortium of researchers a few months ago reported what appeared to be the smallest planet yet detected orbiting a star other than our own sun. Such objects are known as extrasolar planets, or exoplanets, and most of the 300-plus so far discovered are quite large in size compared to Earth. But a new estimate of the size of the smallest exoplanet, known as MOA-2007-BLG-192Lb, reportedly brings its mass down even further—and even closer to that of Earth. (An even smaller object had been observed in 1992, but it orbits a stellar remnant known as a pulsar.)

Astrophysicist Jean-Philippe Beaulieu of the Institute of Astrophysics in Paris, a member of the team that discovered MOA-2007-BLG-192Lb, presented his new estimate at a recent meeting of the Royal Astronomical Society in London, according to the New Scientist. Whereas the original estimate for the exoplanet's mass was roughly three Earths, the new number is a mere 1.4 Earth-masses. (Beaulieu could not be reached for comment today.)

Although seeking out Earth-size planets is considered a prime avenue for discovering habitable worlds, MOA-2007-BLG-192Lb does not appear particularly enticing in that regard. Its host star was originally believed to be a brown dwarf—a failed star too small to initiate fusion. The new data apparently point to a red dwarf, which is somewhat larger and hotter but still far cooler than the sun.

Credit: NASA

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