Fans of Zecharia Sitchin will note that the size of this planet correlates with the often proposed size for the planet Nibiru, of approximately 5 Earth masses.  So at least we now know that such a size is possible for a planet.  This new discovery is also frigid, like 'Nibiru' would be if it lacks the warmth of a parent brown dwarf for company.

Astronomer Paul Kalas has studied proto-planetary discs around extra-solar planets and is joining the growing number of astronomers now convinced that our own Kuiper Belt shows signs of the existence of a hidden binary companion to the Sun. 

Where the Dark Star Theory may appear highly speculative to many, perhaps even nonsensical, it seems as though professional astronomers are becoming increasingly convinced that this object may be for real!  What Paul's proposing is roughly the same as the scenario laid out in my book 'The Dark Star'. 

The problem with drawing parallels between what is going on in the outer Kuiper Belt region and the existence of a Nemesis object as proposed by Muller et al is that these two parts of the solar system are vastly different terrains.  Muller's proposed object is out in the outer Oort Cloud, way too far away to have any affect upon the relatively neighbourly Edgeworth-Kuiper Belt.  Yet when one discusses Dark Star companions one is immediately reminded of the original Nemesis proposition, which is a significantly important idea in the history of Planet X research.

But this proposed companion object would need to reside very much closer to the planetary zone of the solar system to create the effect in the Edgeworth-Kuiper Belt which Paul Kalas, amongst others, is mulling over (5).  I suspect such an object lies between the Edgeworth-Kuiper Belt and the inner Oort Cloud, making it a highly desirable target for discovery in the near future.  More details in my book (see below).

For years we have all been told that the most common type of star system is a binary, where two stars orbit around a common centre of mass in reasonably close proximity.  Our Sun, therefore, is part of a minority community in that it appears to be alone.  As astronomers have become more adept at finding smaller and smaller stars that picture may be changing.  The M-class of star, known as 'red dwarfs', are proper stars, although considerably smaller in size than our Sun.  The population of these types of stars is now known to be very common, and they appear to be mostly singular in nature.

As a result, the statistical populations of known stars have shifted towards singular rather than binary.  But this is just a statistical trick because of the fact that red dwarfs make up the majority of stars.  If you look at larger stars, like our Sun, the binary rule still applies (6).

The other complication to bear in mind is that our appreciation of the populations of brown dwarfs is in its infancy.  Brown dwarfs, which are considerably smaller than even the red dwarfs, may turn out to be just as common.  Not only that, but it may be found that there is a huge swath of companions to all classes of star that take the form of these tiny brown dwarfs. 

Thus, the vast majority of systems may turn out to be multiple star systems, with a main star accompanied by one or more brown dwarfs in wide orbits.  Such a scenario may still be true of our own Sun, a situation which would go a long way towards explaining the enigmatic features of the outer solar system.