We’re closer than ever before to knowing whether there is a ninth planet whooshing around the sun – and, alas, it’s not Pluto.
Planet X, also called Planet Nine, is a hypothetical planetary body seven times the mass of Earth lurking behind Pluto.
If found, this gassy, icy beast some 155 billion miles away from the sun would explain why some objects beyond the Kuiper Belt orbit so strangely.