While scanning the sky for near-Earth asteroids last month, an astronomer made a rare find. On May 10, Brian Skiff of the Lowell Observatory in Flagstaff, Ariz., spied a space rock that takes only 6 months to go around the sun, the shortest orbital period of any known asteroid. With observatory colleagues, Skiff describes the find in a May 14 circular of the Minor Planet Center in Cambridge, Mass.