One such small world is Sedna, a dwarf planet with a highly elongated orbit. "Sedna's orbit is truly peculiar," said Caltech planetary scientist Mike Brown, who led the team that discovered Sedna in 2003.
These extreme orbits, argues Gomes, could be due to the presence of an unknown massive planet. By his reckoning, a planet four times the size of Earth may be out there beyond the orbit of Pluto. In his simulation, he placed the gravitational field of a large planet and watched the effect it had on the SDO's orbits.
"Rodney Gomes is actively seeking further evidence, and I await his findings with interest!" Douglas Hamilton, an astronomer at the University of Maryland, told Life's Little Mysteries. "He has taken on a difficult task, but is taking the right approach. It is definitely a high-risk, high-reward, situation - a discovery of a new planet would be spectacular!"
Although the presence of a massive planet may explain the extreme orbits, there is little else that suggests Planet X 2.0 really is out there. But the method of seeking out other worlds while looking for their gravitational influence on the orbits of other celestial bodies has been done before, with historic success.