Jupiter's gravity has captured two vast swarms of Trojan asteroids at its L4 and L5 Lagrange points, 60 degrees ahead of and behind the planet in its orbit. Numbering well over a million bodies larger than one kilometre, the Trojans are thought to be primordial leftovers from the outer Solar System's formation, trapped during Jupiter's early migration. NASA's Lucy mission, launched in 2021, is now visiting several of them. This scenario includes the ten largest known Trojans — including 624 Hektor and 3548 Eurybates — alongside Jupiter. Their stable co-orbital motion illustrates how a massive planet can permanently corral small bodies in resonant lockstep.