text: what planet is about 40 astronamical units from the sun?   there are no known planets that orbit 40 au from the sun. neptune, the most distant planet, averages just over 30 au.  however, pluto, a dwarf planet (which, somewhat confusingly, isn't a subcategory of planets), orbits between about 29-49 au from the sun, so it averages approximately 40 au.