What in the world did I just see?

So I randomly looked out my window just now... and I noticed the biggest, brightest star (or so I thought) I had ever seen. It was probably about 50x bigger than a typical star. I stared at it for about 3 seconds before it started moving. I then thought, oh it must be a plane. But it didnt move across the sky like a plane does, it seemed to move farther away from earth. It got smaller and less bright for about 10 seconds before completely disappearing into the night. I thought maybe it was a meteor, but shooting stars tend to move much quicker than this did. Any ideas?