such a distant planet has been suspected for some time- big solar system-such a planet 20x farther than neptune -700 au from earth!
takes light 8 min 20sec from sun to reach earth- x700- 97 hours to reach such a planet-but what are u going to do-its 4.22 light years to the nearest star(a dwarf)
plutos diameter is 1473 miles- our moon (unique in relationship to size of its planet) is 2159 mi diameter- 3 other planitesimals like pluto have been discovered


http://www.popularmechanics.com/space/solar-s...ate=071317

http://www.popularmechanics.com/space/solar-s...planet-10/

https://en.wikipedia.org/wiki/List_of_Solar_S...ts_by_size