Bright object seen for several minutes in western sky

My wife and I had driven to Emma Woods Beach to view the sunset because it had been such an incredibly clear day.  There were no clouds in the sky at all.  We arrived at the beach as the sun set and walked out of our car to the beach.  We both noticed a bright object in the western sky approximately 20 degrees above the horizon.  The shape appeared to be well beyond the Channel islands and quite bright.  When we first spotted the object it was heading north west.  We both described it to each other as it turned due west away from the coast.  The profile of the object changed.  There was no trail of exhaust from a rocket or condensation trail from a plane.  It appeared to nearly disappear as it’s profile was headed directly away from us.  In a moment it reappeared as it again angled north west at a slight angle.  I went to our vehicle and retrieved a pair of strong binoculars and the light was gone when I returned, but a mark or line of the object remained in the sky for several minutes as dusk approached.  We both saw this line with the unaided eye and with the binoculars.  It eventually became to dark to see and we returned to our vehicle.  The object seemed many miles away traveling at great speed.  We both have never anything remotely like this before.