My wife an i witnessed a bright star-like object that flashed every 15 to 5 seconds move across the zenith of the night sky (clear night). it traveled from the west to the northwest until it vanished. it appeared almost directly overhead and slightly to the west. it emitted no sound. it changed course a few times but then would resume the general direction. it seemed to speed up and slow down quickly. just before it vanished in the northeast sky it changed course three times to the south then the east and then the north west and then again to the northeast. it would have been mistaken for a satellite except it flashed from 15 to 5 seconds and changed course. it would have been a mistaken for an aircraft except it showed no navigational lights and it changed course on a dime numerous times and sped up and slowed down rapidly.