An international team of scientists including NYUAD researcher Nikolaos Georgakarakos and others from the US, 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. 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. Future models could expand on this work by including additional aspects of the evolution of the Solar System, which could depict it with improved accuracy. This could include simulating the fast migrations of Jupiter at different speeds, and the effects of nearby planets.