Orange orb traveling at low altitude from north to south, seen by three people

Orange orb traveling at low altitude from north to south in a straight line and constant speed. 1,500 - 2000 ft, as fast as a plane or somewhat faster.  No sound at all.  Brighter orange spherical "nucleus" toward front (direction of travel) with less bright orange translucent orb behind.  As it passed, we could see a slight pulsation in the larger orb area, more subtle than a blinking light.  Continued in a straight line until out of sight to the south.