Light object moved slowly from east to west, and disappeared suddenly.My wife and I were enroute to Phoenix from Payson, Arizona, south-bound on the Beeline Highway/Rte 87. On the trip, we both noticed a single non-flashing light. I pointed out to my wife that the object was not in the correct position for Venus. The light travelled from my left to my right over a 15 minute period. I looked at the clock when we first noticed the light, and the time was 19:22. We watched the light until it suddenly disappeared completely.