The asteroid that flew past Earth on Monday has its own moon.
The 230-foot wide moon trailed behind asteroid 2004 BL86, and NASA scientists captured images as it passed. The asteroid and its companion were too far away to pose a threat, flying about 745,000 miles (1.2 million kilometers) from Earth. But it will still be the largest asteroid known to pass this close to the earth until 2027, when an asteroid called 1999 AN10 is expected to arrive.
Asteroid 2004 BL86 will not return to pass by Earth for at least another 200 years, NASA scientists say.
"While it poses no threat to Earth for the foreseeable future, it's a relatively close approach by a relatively large asteroid, so it provides us a unique opportunity to observe and learn more," Don Yeomans said a statement.