Jupiter is accompanied by thousands of smaller celestial bodies, and a similar parade is not seen in the orbit of Saturn: the Solar System’s largest planet appears to be dragging them towards itself. But as you can see, not all of them.

The Trojan asteroids are actually two separate “camps” named after the heroes of the Trojan War, the “Greeks” and the “Trojans”. If we consider the “star-planet” system, then they will revolve around the star, but always approximately orbit the planet, at a certain distance: in front (Greeks) and behind (Trojans).

This is because in these places the gravity of the star and the planet balance each other and the asteroid can stay there for a relatively long time. These locations are called Lagrange points. There are only five of these in any given system. “Greeks” and “Trojans” are ranked fourth (L4) and fifth (L5), respectively.

As the largest planet in the system, Jupiter has the largest “armies”: more than 13,000 in total. Saturn, meanwhile, clearly lacks these: not a single confirmed Trojan or Greek has been observed so far. Astronomers concluded that Jupiter’s gravity did not allow this.

In 2019, asteroid 2019 UO14 was found on the outskirts of Saturn. According to estimates, its diameter can be approximately 6 to 13 kilometers. At that time, researchers could not immediately determine whether it was at one of the Lagrange points. But recently a team of scientists from Canada, the USA, Australia and Macau reported that the asteroid was indeed located at L4. So it is “Greek”, always in front of Saturn. The scientific study prepared about it is published on the preprint server. archive.

Researchers hypothesized that it was actually a centaur asteroid: one of tens of thousands of asteroids scattered in unstable orbits between the orbits of Jupiter and Neptune due to the gravity of the gas giants. According to astronomers, Saturn caught 2019 UO14 at one of its Lagrange points only a few thousand years ago and will “let go” in another millennium. It is worth noting that the status of “Trojan” and “Greek” was generally short-lived by cosmic standards.

Interestingly, scientists suspected that this unusual celestial body contained large amounts of volatile material, and therefore the asteroid may have been exhibiting comet activity. If confirmed, 2019 UO14 would be the first active Trojan (or rather Greek) in the Solar System.