NASA reported October 28 that Lucy had entered the region occupied by Jupiter’s Trojan asteroids after traveling more than 2.2 billion miles. Launched in October 2021, it is approaching the population ahead of Jupiter in its solar orbit.

There is no sharp physical boundary marking this region. Engineers establish Lucy’s position through radio tracking and images of background stars. The spacecraft and its instruments continue operating as expected despite diminishing sunlight and lower temperatures farther from the Sun.

The first close encounter with a Trojan target, Eurybates, is scheduled for August 11, 2027. Reaching the broader region therefore does not mean that the encounter has already happened. Scientists are refining plans for the limited hours available to study the asteroid at close range.

Later visits are planned to Polymele, Leucus and Orus, followed by an Earth gravity assist in 2030 and a journey to the trailing Trojan population. These measurements will help test explanations for how the solar system’s planets formed and moved.