Is there another undiscovered planet lurking in the far reaches of our solar system? Does it follow a distant orbit around the Sun in the mysterious world of comets and other icy bodies? For some researchers, the answer is “almost certainly.”
The case is for The ninth planet (P9) Dating back to at least 2016. That year, astronomers Mike Brown and Konstantin Batygin discovered it Published evidence Pointing out its existence. They and colleagues have published other work supporting P9 since then.
There is a lot of evidence for the existence of P9, but none of it reaches the threshold of conclusive proof. The main evidence concerns orbits Trans-Neptunian extreme objects (ETNOs). It shows a strange cluster indicating a massive object. P9 may be shepherding these objects into their orbits.
The names Brown and Batygin, both astronomers at the California Institute of Technology, appear frequently in connection with P9. Now, they’ve published another paper with colleagues Alessandro Morbidelli and David Nesvorni, providing more evidence supporting P9.
It’s titled “Generation of low-inclination TNO objects and transits of Neptune by Planet Nine.It was published in The Astrophysical Journal Letters.
“The distant regions of the Solar System show a wealth of anomalous dynamical structure, suggesting the presence of a yet-to-be-discovered massive trans-Neptunian body, Planet Nine (P9),” the authors wrote. “Previous analyzes have shown how orbital evolution caused by this object can explain the origins of a wide range of strange orbits.”
To dig deeper into this issue, Batygin, Brown, Morbidelli and Nesvorny examined trans-Neptunian objects (TNOs) with more conventional orbits. They ran N-body simulations of these objects that included everything from the pulls of giant planets and… Hungarian tide For passing stars.
29 objects in the Minor Planet Database have well-characterized orbits with greater than 100 AU, inclination less than 40 degrees, and q (perigee) less than 30 AU. Of those 29, 17 have well-quantified orbits. The researchers focused their simulations on these 17.
The researchers’ goal was to analyze the origins of these objects and determine whether they could be used as probes for P9. To achieve this, they ran two separate sets of simulations. One group with P9 in the solar system and another group without it.
Simulations started in R= 300 million years, i.e. 300 million years of the existence of the solar system. At that time, “fundamental dynamical evolution in the outer solar system was still in its infancy,” the authors explain, while enough time had passed for the population of stars born in the solar system to disperse and for the giant planets to largely end their migrations. . They ended up with about 2,000 objects, or particles, in the simulation with perihelion larger than 30 AU and semi-major axes between 100 and 5,000 AU. This excluded all Neptune-transiting objects from the simulation starting conditions. “More importantly, this choice of initial conditions is inherently related to the assumed orbit of P9,” they point out.
The figure below shows the evolution of some of the 2,000 objects in the simulations.
These are interesting results, but the researchers point out that they in no way prove the existence of P9. These orbits can be generated by other things such as galactic tides. In their next step, they examined the distribution of perihelion.
“Taking into account observational biases, our results reveal that the orbital structure of this group of objects agrees closely with the predictions of the P9 comprehensive model,” the authors wrote. “In stark contrast, the P9-null scenario was statistically rejected at the ~5 level? The level of confidence.”
The authors suggest that something other than P9 could be causing the orbital misalignment. The star was born in a cluster, and the cluster dynamics could have placed these objects in their unusual orbits before the cluster dispersed. A number of rogue Earth-mass planets could also be responsible, affecting the structure of the outer solar system for a few hundred million years before they are somehow removed.
However, the authors chose 17 trans-Neptune objects for a reason. “Because of their low inclinations and perigees, these objects experience rapid orbital chaos and have short dynamical lifetimes,” the authors wrote. This means that everything that pushes these objects into these orbits is ongoing and not a remnant of the past.
An important consequence of this work is that it leads to fallible predictions. We may not have to wait long for the results to be tested. “It is exciting that the dynamics described here, along with all the other evidence for P9, will soon face a rigorous test with the start of VRO (Vera Rubin Observatory),” the authors wrote.
If P9 is real, what is it? It could be the core of a giant planet that was ejected during the early days of the solar system. It could have been a rogue planet that drifted through interstellar space until it fell into the gravitational environment of our solar system. Or it could be a planet that formed in a distant orbit, and was driven into its eccentric orbit by a passing star. If astronomers can confirm the existence of P9, the next question will be: “What is it?”
If you’re at all interested in how science works, the P9 case is very useful. Eureka moments are few and far between in modern astronomy. Evidence builds gradually, accompanied by discussion and counterpoint. Objections are raised and contradictions are pointed out, then methods are improved and thinking develops. What started as one comprehensive question breaks down into smaller, easier-to-answer questions.
But the big question that dominates now, and is likely to continue for much longer: Is there a Planet Nine?
Stay tuned.
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