New planet in the solar system

Description of the orbit of the new planet and associated objects (Batygin & Brown)

This kind of stuff does not happen every day: a new planet 10 times the mass of Earth has been inferred to exist in the outer reaches of the solar system, but has not yet been directly observed. Or has it?

Konstantin Batygin and Mike Brown have deduced (press release, study) the existence of this object from the trajectory of several anomalous transneptunian bodies of the type of Sedna, whose trajectories seem to orbit both the sun and a distant "super-earth" type planet, so remote that it takes 20,000 years to complete an orbit. 

The Caltech team has not directly eyed the object. However...

A Swedish-Mexican team led by R. Liseau pre-published last month a study where they claimed to have directly spotted a possible outer solar system planet. After some controversy the second version of the pre-pub was withdrawn until further data was collected but the first version is still available online. Another pre-pub paper on the same issue was also authored by W. Vlemmings et al., co-authors of the previous one. 

Direct observation of an object that might be a new planet (Liseau et al.)

I do not know yet if the two studies are convergent or rather they refer to different objects. Neither is fully confirmed as of now in any case but something is almost certainly out there lurking in the depths of the Oort cloud.