Galaxy NGC 6240 is said to be in it's million year death spiral, but it is 400 million light years away; does this mean it is already gone? and how high powered a telescope would we need to view it at it's current stages, if it still emits light?  I am slightly curious as to whether one could hypothetically build a telescope that can see previously emitted light by using a telescope that is powered highly enough. 
I am also wondering whether there is any information on galaxies that have collapsed in upon themselves, and have been taken by the black hole at the center of their galaxy that we have legitimate and tangible evidence on.