we were 1 mile south of jim bridger power plant 27 miles east of rocksprings 8500 feet elevation it was star bright no moon yet we did not need flashlights . we were looking at the sky talking about how the sky looked totally clear stars bright by the billions . when all 7 of us at once noticed a large rectagular craft about a1/4 mile wide and 1/2 mile long (may be larger ) . it flew over us at about 5 mile perhour at less than 400 feet . it had a rotation beacon in the center no windows the bottom was dull black . it flew directly over the power plant . no down blast no sound yet we felt a vibrating sensation persons present were myself , shawn whittman , larry thornberry cheslie bolton, sherill love and one other couple . we did not report the event fear of reaction ..