Scientists offer a new explanation for a mystery surrounding Jupiter’s two massive asteroid swarms

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From Tallbloke’s Talkshop

January 21, 2023 by oldbrew

The lead researcher spoke of „a new and natural explanation for the unbiased observation, that the L4 asteroids are about 1.6 times more than the asteroids in the L5 swarm.“ In other words, a ratio of 8:5. In 2018 another team, studying Jupiter’s poles, ‚found an octagon-shaped grouping over the north pole, with eight cyclones surrounding one in the middle, and a pentagon-shaped batch over the south pole. Each cyclone measures several thousand miles (kilometers) across.‘ Again, a ratio of 8:5.
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An international team of scientists, including NYU Abu Dhabi researcher Nikolaos Georgakarakos and others from the U.S., Japan, and China, led by Jian Li from Nanjing University, has developed new insights that may explain the numerical asymmetry of the L4 and L5 Jupiter Trojan swarms, two clusters containing more than 10,000 asteroids that move along Jupiter’s orbital path around the sun.

For decades, scientists have known that there are significantly more asteroids in the L4 swarm than the L5 swarm, but have not fully understood the reason for this asymmetry, says

In the current configuration of the solar system, the two swarms show almost identical dynamical stability and survivability properties, which has led scientists to believe that the differences came about during earlier times of our solar system’s life.

Determining the cause of these differences could uncover new details about the formation and evolution of the solar system.

In the paper, „Asymmetry in the number of L4 and L5 Jupiter Trojans driven by jumping Jupiter,“ published in the journal Astronomy & Astrophysics, the researchers present a mechanism that can explain the observed number asymmetry.

„We propose that an outward—in terms of distance to the sun—fast migration of Jupiter can distort the configuration of the Trojan swarms, resulting in more stable orbits in the L4 swarm than in the L5 one,“ said Li.

„This mechanism, which temporarily induced different evolution paths for the two asteroid groups that share the orbit of Jupiter, provides a new and natural explanation for the unbiased observation, that the L4 asteroids are about 1.6 times more than the asteroids in the L5 swarm.“

The model simulates the orbital evolution of Jupiter, caused by a planetary orbital instability in the early solar system. This led to the outward migration of Jupiter at a very high speed; a migration that the researchers hypothesize was the possible cause of the changes in the stability of the nearby asteroid swarms.

Full article here.
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Talkshop notes, from Wikipedia:

Hilda asteroids — ‚The Hilda asteroids (adj. Hildian) are a dynamical group of more than 5,000 asteroids located beyond the asteroid belt but within Jupiter’s orbit, in a 3:2 orbital resonance with Jupiter.‘

Kirkwood gaps — ‚a gap or dip in the distribution of the semi-major axes (or equivalently of the orbital periods) of the orbits of main-belt asteroids. They correspond to the locations of orbital resonances with Jupiter…The main gaps occur at the 3:1, 5:2, 7:3, and 2:1 mean-motion resonances with Jupiter.‘