The hunt for Planet 9 -- a hypothetical, Neptune-sized object beyond Pluto -- has stirred the scientific community since last year year, when a pair of Caltech astronomers argued in favour of the idea. Those intrepid scientists -- Mike Brown, best known as the guy who killed Pluto, and Konstantin Batygin -- are currently spearheading a search for this elusive giant. Recently, a network of citizen scientists have followed suit. The problem, of course, is we still haven't found it. So what's it going to take?