The world is safe: That 150-foot cosmic rock astronomers were watching hurtled safely past Earth about 2:30pm Eastern. It was the closest known flyby for a rock of its size, passing within 17,500 miles, closer than some satellites. The asteroid was invisible to astronomers in the US at the time of its closest approach, but in Australia, observers used binoculars and telescopes to watch the point of light speed across the night sky. The flyby occurred just hours after smaller meteor exploded above Russia's Ural Mountains. Astronomers say the two events were coincidental.