Earth had a minimoon for nearly three years before it drifted away

Goodnight, moon. Earlier this year, astronomers found 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 spotted a dim object called 2020 CD3 hurtling across the sky in February, they couldn’t be sure if 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.