Recent updates on the Search for Planet Nine

It’s a year since proposed the existence of Planet Nine (1). Despite the fact that its discovery remains elusive, there have been a great many academic papers written on the subject, and no shortage of serious researchers underpinning the theoretical concepts supporting its existence. Many have sought evidence in the solar system which indirectly points to the perturbing influence of this mysterious world; others have provided data which have helped to constrain the parameters of its orbit (by effectively demonstrating where it could NOT be). Throughout 2016, I have been highlighting these developments on the Dark Star Blog.

At the close of 2016, two further papers were published about Planet Nine. The first of these delves more deeply into the possibility that Planet Nine (Brown’s new name for Planet X, which seems to have caught on among astronomers keen to distance this serious search from, well, the mythological planet Nibiru) has a resonance relationship with some of the objects beyond the Edgeworth-Kuiper Belt which it is perturbing. These kinds of resonance relationships are not unusual in planetary orbital dynamics, so such a suggestion is not that odd, even given the eccentricities of the bodies involved here. The new research, from the University of California, Santa Cruz, bolsters the case for this kind of pattern applying to Planet Nine’s orbit:

“We extend these investigations by exploring the suggestion of Malhotra et al. (2016) (2) that Planet Nine is in small integer ratio mean-motion resonances (MMRs) with several of the most distant KBOs. We show that the observed KBO semi-major axes present a set of commensurabilities with an unseen planet at ~654 AU (P~16,725 yr) that has a greater than 98% chance of stemming from a sequence of MMRs rather than from a random distribution.” (3)

Their randomised ‘Monte Carlo’ calculations provide a best fit with a planet of between 6 and 12 Earth masses, whose eccentric orbit is inclined to the ecliptic by about 30 degrees. They are unable to point to a specific area of the sky to search, but provide a broad-brush region which they favour as most probable. Dr Millholland has also helpfully provided a 3D manipulable 3D figure of the cluster of extended scattered disk objects allegedly affected by the purported Planet Nine, alongside their extrapolated orbit for it (4).

The second (now-published) paper, written by Planet Nine advocates Konstantin Batygin and Dr Mike Brown examines in more detail their earlier suggestion that a highly inclined subset of trans-Neptunian objects (TNOs) exhibiting retrograde orbits (namely Drac, Niku, and 2016 NM56) may also owe their odd orbital arrangements to Planet Nine (5). The authors acknowledge the explanatory power of the generally accepted Nice model for the evolution of the solar system into its current format, but also highlight areas which remain unexplained – including these strange TNOs. They tested the possibility that the additional presence of Planet Nine can explain the unusual inclinations of Drac, Niku, 2016 NM56, as well as other members of the currently known trans-Neptunian population which are not well accounted for by the Nice model (6). The paper indicates how many of the solar system mysteries could be readily explained by the presence of a substantial Planet X body.

Such an explanation is not without its critics, as I previously described (5): Critics who will really only be satisfied when this elusive planet is actually found. Dr Mike Brown thinks that should be before the end of next winter (i.e. early 2018), given the number of groups now actively seeking this object (7).

Rogue Planet

How this object managed to end up where it is purported to be continues to mystify astrophysicists. Again, during 2016 I covered a great many of the theories put forward for a world whose orbit keeps it well beyond the solar system’s generally accepted zone of early planetary construction. Indeed, this has been one of the thorniest issues with the whole concept of ‘Planet X’, for decades. Now, new computer simulations carried out by James Vesper and Paul Mason of New Mexico State University support the idea that Planet Nine is a free-floating, or rogue planet, that was captured by the Sun from interstellar space (8):

“…Their simulations showed that 60 percent of the times a rogue planet encountered our solar system, it came in and then left, sometimes taking another smaller planet with it. In 40 percent of cases, however, the rogue was captured and remained in orbit. The simulations also suggested that if such a rogue was captured, it could orbit the sun at the speculated distance and that it was unlikely that a planet any bigger than Neptune has ever entered our solar system—the orderliness of our system suggests it has not been disturbed since the period when the solar system was created.” (9).

One might argue that with these computer simulations you tend to get out what you put in. Nonetheless, these support the capture scenario, and potentially align the proposed Planet Nine ever closer to Zecharia Sitchin’s mythological Nibiru/Marduk Planet X. Why? Because his books not only describe a Planet X body of about 10 Earth masses in an elliptical orbit inclined 30 degrees to the ecliptic (as per Planet Nine) but also pinpoint its origin as being just such a rogue planet captured by the Sun from interstellar space (10).

There remain two stark differences: The first is that Planet Nine is thought to remain well beyond the heliopause for the entire duration of its eccentric orbit. This contrasts with Nibiru’s asteroid belt-skimming perihelion passage (but these days, with a known second asteroid belt in the form of the distant Kuiper Belt beyond Neptune, one could imagine a slightly different reading of the Babylonian ‘hammered bracelet’ from Enuma Elish?). The second is that Planet Nine’s projected orbital period is 10 – 20,000 years, contrasting with Sitchin’s 3,600 years.

Still, enough similarities to make any number of scientists feel acutely uncomfortable – if not a little irritated.