White round light, high in northwest sky. Brighter than Jupiter. Slowly shrank to the size of satellite, then moved to the northwest.

I saw a bright light high in the north east sky. It was white and perfectly round.
I could see Jupiter and the constellation of Orien. I know this light was not Sirius or Jupiter.
The magnitude was at least double that of Jupiter and at least three times the diameter.
As I watched over a period of 10 seconds, the light shrank until it became the size and brightness of a satellite.  I watched as it moved to the northwest.  It looked exactly like a satellite as it moved into shadow.  My impression was that it must be a satellite, but what caused the light?