May be of interest: https://en.wikipedia.org/wiki/Halton_Arp https://en.wikipedia.org/wiki/Halton_Arp https://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies

May be of interest: https://en.wikipedia.org/wiki/Halton_Arp https://en.wikipedia.org/wiki/Halton_Arp https://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies https://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies I don't know whether or how all his observations have been explained, but they may give a good starting point for research. Either way, an atlas of peculiar observations is a good thing. Producing something like that may be worthwhile for other areas of research as well.