An asteroid speeding across the Northern sky will make its closet approach to Earth in more than 80 years Monday night -- and even then it will be farther away than the moon. Scientists say the rocky object, known as 2004XP14, poses no threat to the planet; it can't be seen by the naked eye. And because it is flying at a speed of nearly 11 miles a second -- nearly 4,000 mph -- it should prove an elusive target for even the best of amateur astronomers, even those armed with high-powered telescopes. John Giorgini, an astronomer and analyst with NASA's Near Earth Object Program at the Jet Propulsion Laboratory, said the asteroid should be rising above the eastern portion of the northern horizon of the Bay Area at about 11 p.m. Monday. It will remain in the sky all night, he said, as it passes through the constellations Cassiopeia, Cepheus and Draco before the dawning sun washes out the dark night sky.