Planet Nine: Are They Digging in the Wrong Place?

Last month, scientists working on the Outer Solar System Origins Survey (OSSOS) published a large dataset of new Kuiper Belt Objects, including several new extended scattered disk objects discovered way beyond the main belt (1).  These four new distant objects seemed to have a more random set of properties, when compared to the rather more neat array of objects which had previously been constituted the Planet Nine cluster.  This led to scepticism among the OSSOS scientific team that there was any real evidence for Planet Nine.  Instead, they argued, the perceived patterns of these distant objects might be a function of observational bias (2).

Whilst reporting on these new discoveries and their potential implications, I predicted that the debate was about to hot up, bringing forth a new series of Planet X-related articles and papers (3).  Indeed, leading outer solar system scientists were publishing related materials in quick succession (4,5), each finding new correlations and patterns which might indicate the presence of an unseen perturbing influence.


Now, Caltech’s Konstantin Batygin has published an article analysing the impact of the discovery of these new extended scattered disk objects on the potential for a Planet Nine body.  The short conclusion he draws is that although the objects are, on the face of it, randomly distributed, their property set is largely consistent with Caltech’s original thesis (6).  They are either anti-aligned to the purported Planet Nine body (as the original cluster is thought to be), or aligned with it in a meta-stable array.

The one object which is completely off-kilter, 2015 GT50, turns out to have a resonance relationship with a set of values for the unseen Planet Nine object, as described in the original 2016 Caltech paper (7).  At least, that’s what Dr Batygin argues.  Others may sense a circular argument here, whereby a cluster of objects points to a set of parameters for the mystery perturber, whose theoretical orbital characteristics can then be used to explain a data point that fits neither the anti-aligned nor the aligned cluster :

“A more cursory inspection  (sic) of the above plot however, brings to light the existence of a string of specific orbital radii that correspond to resonances with Planet Nine, where the simulated objects circulate through the full 0-360 degree range of orbital orientations. Remarkably, the outlier (2015 GT50) falls *exactly* on one such orbit (i.e. note on the plot above that the gray point falls on a vertical blue line). 


“This is kind of staggering. Without changing the Planet Nine parameters at all (to make this plot I’ve adopted the same a=700AU e=0.6 m=10Mearth P9 configuration as in the original Batygin & Brown 2016 AJ paper), the model manages to fit all the data, including the supposed outlier” (6)

Dr Batygin goes on to say that the cluster effect is just one of five lines of enquiry pointing towards the existence of a super-Earth Planet X body.  Even if the cluster argument is weakened by the new OSSOS dataset of objects (he doesn’t agree that it is), there is still compelling evidence for Caltech’s ‘Planet Nine’ object, he argues, including the mystery of the retrograde Kuiper Belt Objects Niku and Drac (8).  The mechanism put forward last October for Planet Nine to generate these anomalies (9) can be successfully applied to two new objects within the OSSOS dataset (10), Batygin argues.

It’s good to see these arguments being thrown about so quickly, and within a public domain.  Journal publications will no doubt follow, but such is the heat generated by the Planet Nine debate that there is little patience to wait for these publications, and more formal conference discussion that follows.  Or else, science’s battlefields are modernising on competing blogs.  To some extent, I welcome this, because it provides welcome clarity and speed to this debate, wrapped up in an informed, but relatively understandable, format.  It is clear that the Caltech team seem unperturbed by the new OSSOS data, and ensuing scepticism about Planet Nine.  But none of this counter-argument is peer-reviewed, yet.


There’s one last issue I would like to point out here, above and beyond the existence of Planet Nine debate.  Let’s say the extended cluster does indeed point towards a Planet X body.  The original cluster was very one-sided, and the Caltech team interpreted that as being the dynamically stable ‘anti-aligned’ orientation to Planet Nine.  in other words, the bulk of Planet Nine’s eccentric orbit lies in the opposite hemisphere of the solar system than the bulk of the extended TNO orbits within the cluster.  In the orbital diagram (above), the original – and now enhanced – cluster is seen in purple.

Now we have two data points (seen in green in the diagram) which fall into the ‘meta-stable’ aligned cluster, as noted by Dr Batygin (6).  Given the discussion about observational bias, it seems perfectly possible to me that as more discoveries are made, the population of this side of the fence will grow.  Perhaps, in time, this side of the fence will be the dominant sector.  In which case, it may be that the Caltech team have misinterpreted the initial data set as anti-aligned, when they are actually the meta-stable aligned grouping.  I argued this early last year, citing evidence that Planet X is located in the opposite part of the sky to Caltech’s preferred location in Orion (11).

Of course, it’s too early to say based upon just two new objects, but if that’s the case, then, in the immortal words of Indiana Jones, “They’re digging in the wrong place!”


Written by Andy Lloyd,  3rd July 2017


1)   Cory Shankman et al “OSSOS VI. Striking Biases in the detection of large semimajor axis Trans-Neptunian Objects”, 19th June 2017, accepted for publication by the The Astronomical Journal,

2)   Josh Sokol “New haul of distant worlds casts doubt on Planet Nine”, 21st June 2017

3)  Andy Lloyd “New Arguments about Planet Nine Cluster” 23rd June 2017

4)  Volk, K. & Malhotra, R. “The curiously warped mean plane of the Kuiper belt”, Astronomical Journal, (in press) (2017)

5)   C. de la Fuente Marcos & R. de la Fuente Marcos “Evidence for a possible bimodal distribution of the nodal distances of the extreme trans-Neptunian objects: avoiding a trans-Plutonian planet or just plain bias?” 21 Jun 2017, Accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters,

6)  Konstantin Batygin “The Search for Planet Nine: Status Update (Part 1)” 30th June 2017

7)  K. Batygin & M. Brown “Evidence for a Distant Giant Planet in the Solar System” 20th January 2016, The Astronomical Journal, Volume 151, Number 2,

8)  Andy Lloyd “Niku, Drac and L91 Perturbed by Planet Nine…or Something Else?” 18th October 2016

9)  Konstantin Batygin & Michael Brown “Generation of Highly Inclined Trans-Neptunian Objects by Planet Nine” 17th October 2016

10)  Konstantin Batygin “The Search for Planet Nine: Status Update (Part 2)” 2nd July 2017

11)  Andy Lloyd “Planet Nine Constellations Predicted by Sitchin, and IRAS” 26th January 2016

Image credits: Konstantin Batygin/Caltech

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