If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck.
The famous “Duck test” is accepted in many different fields, even though this kind of abductive reasoning does not positively prove its conclusion. The same could be said of another well-accepted practice – computer modeling and simulations. In other words, if the model says it’s a duck or a majority of the simulations say it’s a duck, then it’s probably a duck. This is a good place to start with a new simulation which shows that there’s probably an Earth- or Mars-sized planet orbiting beyond Neptune that was possibly pushed to the nether regions of the solar system by its giant gassy planets. Should we believe them … or duck when we question them?
Wait a minute! Are these simulations saying Planet Nine is not a giant but merely the size of Earth or Mars?
No, they’re not calling this duck Planet Nine … yet. Nor are they calling it Pluto’s Replacement Which Fits the Standard Planetary Size Criteria. Brett Gladman from the Department of Physics and Astronomy at the University of British Columbia, and Kathryn Volk of the Lunar and Planetary Laboratory at the University of Arizona co-authored “Transneptunian Space” for the Annual Review of Astronomy and Physics in which they explain why the outer reaches of the Solar System need another planet.
"It seems unlikely that nature created four giant planet cores, but then nothing else larger than dwarf planets in the outer solar system."
Many astronomers who don’t believe there’s a giant Planet Nine are nonetheless puzzled at there being only four small rocky planets and four gas giants in our solar system. Systems that can create those eight should have created more rocky planets beyond the gassy four, or even between two of them. It seems more likely that #9 was a Mars clone rather than a giant Planet Nine. But … if we can find little rocks like Pluto, Sedna, Eris and others, why haven’t astronomers located this bigger one?
“Our simulations found that in about half of the cases, all of the Mars-scale planets in the outer Solar System were ejected into interstellar space. But in the remaining half, one ‘rogue’ planet was left in an orbit similar to that of the detached population of Kuiper Belt objects.”
In another simulation reported in Inverse, astrophysicist Scott Tremaine found a case for a rogue rock planet that might have been moved from between the gassy giants to the area beyond them by the gassy giants themselves. It’s not so farfetched – astronomers agree that the planets, especially the gas giants, have moved around. However, it is farfetched that it hasn’t been discovered yet. All we have to go on so far is gut feelings, models and simulations, and the hope that stronger telescopes can get enough data from those sources to located the medium-sized remote planet – or prove the models wrong.
For now, it’s not yet a duck. Or a mini-Planet Nine either.