MSNBC reports that two sets of researchers have come to the same conclusion - there is a giant planet or failed star in a 4-6 million year orbit around the Sun, 800 times further away than Pluto. When the Space Infrared Telescope Facility is launched next year it might be able to spot it.

"Some theorists have proposed that the gravitational effect of a massive unseen object in a distant orbit — nicknamed “Nemesis” or the “Death Star” — could set off periodic cometary storms, which would increase the chances of a catastrophic impact with Earth."