I could be mistaken here, but I did glean from somewhere (probably the net) that gazing up at the night sky doesn't reveal the full picture about the many faint celestial objects that may be lurking unseen in nearby space - that is to say, the space between the Centauri system and the outer margins of our Oort Cloud. These objects might range from Neptunian gas giants, through to low-mass brown dwarfs, and maybe even one or two extremely dim red dwarfs? I mention the above in passing because I would like to know just how far (preferably in terms of AU rather than light-years and parsecs) our most powerful telescopes are able to detect such "nearby" objects. I guess the answer would depend in part on luminosity, albedo and angular size. Nevertheless, I would appreciate some kind of yardstick when when it comes to understanding the current resolving power we can bring to bear on any sizeable object beyond (say) the Kuiper belt. Many thanks.