Gravitational interaction, not giant planet, may explain unusual TNO orbits

'Planet 9' might really be a gang of asteroids shooting comets at us

'Planet 9' might really be a gang of asteroids shooting comets at us

The odd orbits of TNOs are a result of what the researchers call "collective gravity".

Though no evidence suggests a ghostly planet exists in our stellar system, theories of the hypothetical planet, which is said to be 10 times the size of Earth, have been doing rounds for nearly two years.

Of course, Planet Nine may simply not exist, and this is where the new hypothesis comes in.

Planet Nine was first hypothesised in 2014, when researchers noticed that some of the space rocks out past Neptune, known as trans-Neptunian objects (TNOs), have unusually looping orbits, "detached" from the strong gravitational influence of the larger gas giants in the Solar System.

More importantly, the work could also shed some light on the catastrophic demise of dinosaurs on Earth.

[O] bservations suggest that there is a large population of detached TNOs that have a dynamical history different than that of the objects scattered by Neptune.

In the latest study, presented this week at a meeting of the American Astronomical Society, astronomers looked at new models depicting how the massive swarm of objects that make up the Kuiper Belt orbit the sun.

The most likely culprit, the researchers concluded, was the tug of gravity from a large, undiscovered planet.

The researchers calculated the mass of hundreds of trans-Neptunian objects and discovered that it wouldn't be a stretch for similar bodies to create enough gravitational pull to yank objects as large as dwarf planets into weird orbits.

"You see a pileup of the orbits of smaller objects to one side of the sun", Fleisig said. "These orbits crash into the bigger body, and what happens is those interactions will change its orbit from an oval shape to a more circular shape".

Not everyone is convinced that this "self-gravity" story explains the motion of detached objects. This means that the Kuiper belt objects might not exert enough gravity on each other for the orbital effects observed.

Co-author Ann-Marie Madigan of the University of Colorado Boulder said, 'There are so many of these bodies out there. Modeling such a complex system as the Kuiper Belt is enormously expensive, and past researchers did not add in the masses of as many objects. Over time, this could have caused the larger TNOs with their unusual, highly elliptical orbits, to "detach" from the rest of the solar system. There's no explanation for why the orbits of the various detached TNOs all tilt the same way, for example. This cycle could be responsible for shooting comets in our direction every 30 million years or so and might even explain the large space rock that's believed to have ushered dinosaurs off the evolutionary stage.

These groupings of distant asteroids and other small objects could also interact with comets lurking out on the chilled edges of our solar system, tightening and widening their orbits over and over again.

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