ufo seen from my window on the penthouse floor

All of a sudden I looked at my large window {i live on the penthouse floor} and saw a perfectly round white object going in west. It was to slow to be a meteorit or comet and to fast to be an airoplane or hellicopter.I have seen meteorits from my window in the past and they wiz past usually going north and they have a tail,This object was big enough to make out it was round.It didn't glow or have any sound
I thought about it after I saw it,I had never seen anything like that before. What really stands out when I think about it is that i could make out the shape to be round.I live in N.D.G. montreal