Weird Orbits of Distant Objects Can Be Explained Without Invoking a 'Planet Nine'

schwit1 shares a report from Space.com: The weirdly clustered orbits of some far-flung bodies in our solar system can be explained without invoking a big, undiscovered 'Planet Nine,' a new study suggests. The shepherding gravitational pull could come from many fellow trans-Neptunian objects (TNOs) rather than a single massive world, according to the research. 'If you remove Planet Nine from the model, and instead allow for lots of small objects scattered across a wide area, collective attractions between those objects could just as easily account for the eccentric orbits we see in some TNOs,' study lead author Antranik Sefilian, a doctoral student in the Department of Applied Mathematics and Theoretical Physics at Cambridge University in England, said in a statement.

The duo's modeling work suggests that the strength-in-numbers explanation does indeed work -- if the mass of the Kuiper Belt, the ring of bodies beyond Neptune, is a few to 10 times that of Earth. This is a pretty big 'if,' given that most estimates peg the Kuiper Belt's mass at less than 10 percent that of Earth (and one recent study put the figure at 0.02 Earth masses). But other solar systems are known to harbor massive disks of material in their outer reaches, Sefilian and Touma noted. And our failure to spot one around our own sun doesn't mean it doesn't exist, they stressed. The new study has been accepted for publication in the Astronomical Journal.

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