by More evidence for a hypothetical addition planet lurking in the farthest reaches of us Solar system has come to light — and the clues relate to icy bodies that cross the orbit of the Neptune while traversing long winding paths around the sun.
Planet Nineas the predicted planet is referred to, was first posted in 2016 by Caltech’s Konstantin Batygin and Michael Brown, the latter of whom received the dwarf planet Eris in 2005. Their original evidence focused mainly on the cluster of trans-Neptunian objects (TNO), which are objects that spend most of their orbits further from the Sun than Neptune. That’s it enough much. Specifically, the duo had zoomed in on TNOs that had high inclinations, meaning the objects orbited the Sun at steep angles to the ecliptic plane.
Because the material of the solar system formed from a disk around the sun, we would expect the orbits of everything in the sun’s orbit to be relatively close to the plane of that disk. However, some do not – and this is understood by the team as evidence that Planet Nine is on gravity which may be pulling the objects out of the ecliptic and dividing them into highly inclined orbits like “apsides” (nearest and farthest points in their orbits around the sun) and oriented with seem to tilt away from the ecliptic.
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However, some astronomers were skeptical, arguing that what Batygin and Brown saw as a clustering illusions due to observational bias. The Caltech duo dispute this, and have now published a paper that focuses specifically on observations of low-bias TNOs that have not clustered, but still have characteristics.
These icy TNOs are peculiar because they spend most of their lives hundreds of times further from the sun than World but their orbits are so long that they pass in and spend a short time closer to the sun than Neptune, which is only 30 times farther from the sun than Earth. “With this work, we looked at objects with long-period orbits but strongly interacting with Neptune, especially those that cross Neptune’s orbit,” said Batygin space.com.
This does not include everything that crosses Neptune’s orbit, to be clear. Pluto is a good counterexample. Like Pluto, most TNOs do not have orbits as long as those included in the team’s new research. Rather, most TNOs have trajectories that keep them fairly close to Neptune for long periods of time. time so that they can be controlled by the ice giant’s gravity.
However, the team only touched on those TNOs that receive hundreds astronomical units away from Neptune’s gravitational tides, where Planet Nine can influence them — if it exists, of course. Because these studied objects come from all directions close to the ecliptic plane, showing no clustering behavior, the same bias claim is balanced by previous evidence for high-bias, clustered TNOs.
The TNOs studied, and none on similar paths, do not spend too much time in orbit; Over millions of years the gravity of the azure blue ice giant Neptune inevitably bats them, scattering them far and sometimes even out of the solar system completely. This means that whatever sends GNPs into a transiting Neptune orbit is continuously being done. An ongoing process must be in place to replenish the TNO supply. This means that the culprit cannot be something that happened in the distant past, like a star passing by in particular. It must still be a thing.
There are two situations that could regularly put TNOs on long, looping orbits that cross Neptune’s path. One case is the galactic tide, which is the gravitational force of the tide The Milky Way Galaxy all around us acting on things within the Oort cloud, which lies far beyond Neptune. These objects only feel the Sun’s gravity due to their distance from our host star, but the Galactic tide can bring them closer to Neptune.
The other scenario — perhaps the most interesting — is that the gravity of Planet Nine is affecting these Oort Cloud objects enough that they move closer to Neptune over time.
Batygin and his team—Michael Brown, Alessandro Morbidelli of the Observatoire de la Côte d’Azur in Nice, France, and David Nesvorny of the Southwest Research Institute in Boulder, Colorado—conducted two sets of simulations using real observational data, GNPs which transits low Neptune to find out which situation is more accurate.
One simulation involved a planet with five times the mass of Earth impacting the TNOs (the simulated properties they used for Planet Nine were derived from the properties best explained by previous evidence such as the cluster of high affinity TNOs) , and the other the simulation had no Planet Nine at all and only modeled the Galactic tide. Which would be better able to get TNOs to pass Neptune?
The simulations showed that low-inclination TNOs can only regularly enter Neptune’s orbit if Planet Nine is indeed there to slingshot them. On their own, the margins of galactic tides were considered too weak to detect TNOs beyond Neptune. So, in the simulation of galactic tides, the TNOs arrive within a certain distance from the sun and no closer – but in the case of Planet Nine, the TNOs are spread over a range of orbits crossing Neptune, which matches what we see in reality. .
“We show that you can reject the case where this is happening because of the galactic tides with amazing statistical significance,” Batygin said. “On the contrary, the Planet Nine case fits the data perfectly.”
Batygin compares it to a football game (soccer, reading you Americans), where Neptune is the goalie. The galactic tides can shoot the TNOs towards the goal, but not enough oomph to get them past the goalie. Planet Nine, on the other hand, is like a planetary Harry Kane, regularly shooting the TNOs past Neptune with finesse.
“What we see in the data is a lot of football inside the goal,” said Batygin.
However, the pursuit of the football striker continues.
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Later this decade, the Vera Rubin Observatory in Chile that will open and begin a nighttime, all-sky survey with its 8.4-meter mirror telescope. It will be able to test the evidence for Planet Nine available so far — the cluster of orbits, the alignment of their orbital planes, their steep orbital inclinations, and the prevalence of retrograde (backward orbits) Centaurs. These refer to icy bodies that came in from the Oort Cloud and are currently orbiting among the outer planets of the solar system. If any of these are illusions due to observational biases, then the Vera Rubin observations will show them to be. Although contrary, it could strengthen the evidence, and find many more TNOs that show the same potential impacts as Planet Nine.
“It will test all these lines of gravitational evidence with a new independent survey that is not subject to the same biases as the previous ones,” Batygin said.
The Vera Rubin Observatory may even go all the way and get the big tamale.
“By virtue of his efficiency, maybe—just maybe—he’ll find Planet Nine,” Batygin said. “That would be pretty cool.”
The new results have been accepted for publication in The Astrophysical Journal Letters, and are currently available as a preprint.
