The largest object to be discovered in the Solar System since Pluto was found in 1930 was spotted by a sky survey on Tuesday.

News of the hulking object leaked out on Thursday before the researchers at Caltech could pin down the giant's size and orbit.

Tentatively called 2004 DW, the object lies beyond Neptune in the mysterious Kuiper Belt. This shadowy belt is a collection of primordial icy bodies which circle our Sun and are thought to be the remnants of planetary formation.