The asteroid was its closest on Monday morning , but the best viewing was Monday night . Asteroid 2004 YU55 is about 3 1/2 times as wide and probably a mile in diameter. BL86 came about 745,000 miles ( 1.2 million kilometers ) from Earth , or about three times as far away as the moon , just after 11 a.m . ET Monday , according to NASA . NASA photos released Monday show small moon orbiting the asteroid .
The asteroid was its closest on Monday morning , but the best viewing was Monday night . Asteroid 2004 YU55 is about 3 1/2 times as wide and probably a mile in diameter. NASA photos released Monday show small moon orbiting the asteroid .