4581 ASCLEPIUS

'4581 Asclepius' is a small asteroid of the Apollo group that can approach Earth’s orbit to within 600,000 km; it was discovered in 1989 by the American astronomers Henry E. Holt (1929-) and Norman G. Thomas (1930-). Asclepius (1989 FC) passed by the Earth on March 22 1989 at a distance of some 700,000 km, causing some media attention at that time.
Astronomers say had the asteroid hit Earth, the impact would have been equivalent to 1 Hiroshima-sized atomic bomb detonating every second for 50 days. Subsequent discoveries revealed that a whole class of such objects exists, and that an object the size of the one which just missed Earth in March, 1989, probably comes by undetected once every two or three years. "On the cosmic scale of things, that was a close call," said Dr. Henry Holt.