Glowing orb hovering low beside highway. Seemed to follow us from behind then disappear.

We were driving along a highway and saw a bright, stationary, low hovering craft in a valley to the side of us.  It was abnormally bright, blinding almost. Spherical in shape and glowing a white/blue colour.  We slowed down and wanted to pull over to take a photo but the roadways were too busy to stop safely.  As we slowed, we noticed the object appeared as if it was looking for something on the ground.  We passed it to our right.  We then watched it slowly approach us from the rear window of the car.  The children became frightened and said “its following us, what is it!”  I looked back again but did not see it this time, just as the children screamed out “whoa it just disappeared.”