According to Scientific America, an article from Astronomical Journal suggest the likelihood of a 9th planet (come on, let's just say Pluto is a planet, okay?), gravitational signature of a gaseous giant that is ten times bigger than earth in terms of mass.
This totally vindicates science fiction writers were ridiculed for writing about aliens from the 9th or even 10th planet. Totally "hand to the face" to those invaders-only come from Mars camp.
Some possible basic characteristics of this yet to be seen or named 9th planet includes a 20,000 years orbit around the same sun we orbit and it is considered to be a super-earth being three times as big as our world.
Of course, we have no idea what is out there and our scientific data can only be augmented over years and decades as we send probes further out of our solar system. This discovery of the 9th planet was not viewed through a telescope but rather through modeling of how its gravitational signature affected the movement of nearby objects.
So, expect more on this, lots of media coverage on trying to give it a name, and lots more discoveries in the near future.