CHINA might have its sights set on the moon (see left), but astronomers are on the look out for alternatives. Earlier this year, they spotted a minimoon orbiting Earth. It has now drifted away, but we should soon be able to detect more of these miniature companions. When astronomers at the Catalina Sky Survey in Arizona sported a dim object they called 2020 CD3 hurtling across the sky in February, they couldn't be sure whether it was a minimoon or an artificial object like a rocket booster. Over the following few months, Grigori Fedorets at Queen's University Belfast in the UK and his colleagues used a series of telescopes around the world to take more measurements of the object and figure out what it was.
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