re: exoplanets around PWD's
Telescopes don't have to be physically large, if the optical interferometry is wel mastered! We could combine a large number of them, not physically linked. (That is an argument for a Moon return, well, just one of them and as a way to begin develop this technology).
Meanwhile, if we're interested in merely detecting exoplanets, the Pulsating White Dwarfs might make it easier.
Planets that remain as such even after their sun has undergone an energetic death!
Raoul