Bright spherical object was moving from south to north at about 5,000 feet in altitude; very high rate of speed. Size of the object was difficult to estimate.During it's observed trajectory of what looked like level flight, the object disappeared about 2/3rd's of the way in its' flight path. There was no sound of any kind during observation.The night visibility was very good, no cloud cover, moon was in an early-crescent and low light configuration.Object did not exhibit a 'tail' of any kind, so it was not mistakened as a 'reentering body'.This was clearly an object of intelligent design, traveling at a very high rate of speed, making no sound whatsoever and then it literally 'blinked off' before it had completed what would have been a continuing path of flight over the horizon.I live within a few miles of a nuclear power plant, which is in the same vicinity as the direction of the object and in the general area where the object disappeared from view.There were no other aircraft of any kind in the area.