More than three dozen asteroids have flown closer to Earth in the past few years, but scientists believe 2004 XP14 is among the largest.
The asteroid, discovered in 2004, is estimated to be up to 800 metres wide based on its brightness. Late Sunday and early Monday, it was expected to be visible as a small moving dot to amateur sky watchers with good telescopes in North America and as a fainter object in Europe. Its closest approach was over the U.S. West Coast.
Scientists estimate 2004 XP14 will have 10 more close encounters with Earth over this century, none expected to pose a threat to the planet.