New simulations indicate that Jupiter was formed four times further from the sun than its current position and was a rocky planet similar to Earth in size. Jupiter also has two groups of thousands of asteroids following and trailing it, in the same orbit. The simulations show that the Trojan asteroids were drawn in when Jupiter was a young planet with no gas atmosphere, which means that these asteroids most probably consist of building blocks similar to those that formed Jupiter’s core. In 2021, NASA’s space probe Lucy will be launched into orbit around six of Jupiter’s Trojan asteroids to study them.
https://phys.org/news/2019-03-jupiter-unknown-journey-early-solar.html