Gigantic hidden planet could be hurling comets at Earth

Following up on our Dec. 6 article ("'Dark Jupiter' may haunt the edge of the solar system"), we bring you word from University of Louisiana-Lafayette astrophysicists John Matese and Daniel Whitmire. From io9.com:

Far away in the frozen outermost depths of our solar system, there might be a hidden planet four times the size of Jupiter. This secret companion to the Sun could be responsible for sending comets into the inner solar system.

This idea is an intriguing variation on the old Nemesis theory, which holds the Sun has a smaller companion star orbiting the outer reaches of the solar system. The Nemesis star was thought to be either a pint-sized red dwarf of a failed brown dwarf, and either way its movements through the Oort Cloud at the furthest edge of our solar system would cause comets to hurtle out of their obits. Some of these would hit Earth, leading to mass extinction events. The presence of Nemesis would explain why these extinctions occur in an apparently cyclical fashion.

That's the old theory, which fell apart because (among other things) it turns out Nemesis could not have a stable enough orbit to account for the regular mass extinctions, which is the main reason such an object was hypothesized in the first place. But now University of Louisiana-Lafayette astrophysicists John Matese and Daniel Whitmire have a new theory that holds a rather different kind of companion object is out in the Oort Cloud. Fittingly, they've named it Tyche, who in mythology is the good sister of the evil Nemesis.

You can read more here.