Large bright light that shrank until gone

About 3 O Clock this morning myself and Himself went outside for a cigarette before bed and were looking up.I said " See that,that's a planet,you can tell because it's not twinkling.I wonder which one it is?" Then it started shrinking! It got smaller and smaller until it nearly disappeared and was just very faint,then it disappeared altogether.
We are sceptics.I have always said I won't believe in aliens until I meet one face-to-face,shake it's hand and it takes me to it's planet,shows me round and gives me my dinner! But we both saw it and planes and satellites don't do what this thing did.We haven't got smart phones so we couldn't photograph or film it.