An asteroid estimated to be as big as 2.5 miles wide will fly by Earth next month, but won't hit us, scientists at NASA said Tuesday. CNN reports that the asteroid called 52768 (1998 OR2) will pass within 3 million miles of Earth, while traveling at close to 20,000 miles per hour. NASA's Center for Near Earth Object Studies says it will make its flyby on Wednesday, April 29, at 4:56 a.m. ET.