Move Over Pluto: There's a New Planet 9 in Town

Personally, I’ve always lamented the loss of Pluto as a ‘real’ planet.   Losing Pluto is like losing a close friend who, despite ...

Personally, I’ve always lamented the loss of Pluto as a ‘real’ planet.  Losing Pluto is like losing a close friend who, despite knowing they weren’t good for you, you wanted to hold on to for ‘old times’ sake’. Fortunately, just as we find ourselves moving on from our weird planet-human relationship with ex-Planet 9, a new prospect emerges on the horizon. Or rather, a prospective prospect. Researchers believe that they have evidence of a new, better, larger Planet 9, one that would (for the sake of our gentle hearts) not be torn away from us the way Pluto so cruelly was.  In a twist of fate, one of the lead researchers to make this as of yet unconfirmed discovery is the self-proclaimed ‘Pluto-killer’ himself, Dr. Mike Brown at Caltech.  Well, well, well, Mikey, looks like someone’s come crawling back.   All jokes aside, astronomers Batygin and Brown have recently published in The Astronomical Journal describing their analysis of distant orbit patterns that they say point to the existence of a new Planet 9, this one far more massive than Pluto.

The Kuiper Belt, a region of space extending roughly 30-50 AU from the sun (Earth is roughly 1 AU from that shining beacon in the sky), is the cold, dark place beyond Neptune where Pluto and several other dwarf planets are known to hang out. The Kuiper Belt consists largely of small bodies thought to be remnants of the formation of our solar system. Astronomers have known for some time now that there are several distant Kuiper Belt Objects (so-called ‘KBOs’) whose orbits appear clustered together and closely related, although no successful theoretical model had yet been proposed to account for these somewhat odd observations.  Batygin and Brown point out that in light of the tightly confined perihelion* positions and orbital planes of these KBOs, the likelihood of such clustering behavior being due entirely to chance is only about 0.007%, indicating the need for an external force to account for their behavior.

With these curious observations in mind, Batygin and Brown set out to identify a physical cause for these unaccounted for patterns in KBOs.  The authors were able to conclude, based on a series of calculations and simulations, that a large planetary body with an extended orbit (10,000-20,000 years) could appropriately explain the oddly correlated movement of the KBOs. Furthermore, simulations have suggested that the body causing such a perturbation of gravitational orbits would need to be rather massive, certainly massive enough to be considered a proper planet.

Although not yet substantiated, the proposed existence of a new and improved Planet 9 could lead the actual observation of this new planet sooner rather than later or never. I guess this is also a good lesson for any ex-Pluto enthusiasts out there; there are always more planets in the sky.


Batygin, K., and Brown, M.E., Evidence for A Distant Giant Planet in The Solar System, The Astronomical Journal, 2016, 151, 1-12. DOI:10.3847/0004-6256/151/2/22
*Perihilion: point in a planet’s orbit at which it is closest to the sun.

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