About one out of every eight asteroids orbiting near Earth travels with a companion. Scientists have come up with that estimate by observing near-Earth asteroids, rocks that cross Earth’s orbit, with the two most sensitive radar telescopes ever built. Some 16 percent of near-Earth asteroids larger than 200 meters across travel with a companion, report Jean-Luc Margot of the California Institute of Technology in Pasadena and his colleagues in the May 24 Science.
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