Under the name of 2019 LD2, stationed within Jupiter’s orbit, astronomers have identified a unique object, the first of its kind, halfway between a comet and an asteroid. It is the only active Jupiter Trojan known to science.
When we talk about Trojans in space we are referring to a group of asteroids located on the same orbital path as Jupiter, an astronomical object that belongs to a large group of objects that shares the orbit around the Sun of the planet Jupiter. However, until now they were dead objects, inert asteroids… until the arrival of 2019 LD2.
The Institute of Astronomy at the University of Hawaii, who have issued a statement, says that the object has a tail very similar to a comet. So, comet or asteroid? The truth is that there is an intermediate class of objects known as active asteroids. They are asteroids that have suddenly come to life, and 2019 LD2 points to it.
Discovered in June last year by astronomers from the University of Hawaii’s ATLAS, a space that is generally used to find Earth-threatening objects, when its blurred appearance was first detected, it raised suspicions that it could indeed be a comet or something. very similar.
The second set of ATLAS observations in July 2019 strengthened this idea, with images revealing a wispy comet-like tail, likely composed of gas and dust. Subsequently, late last year and early 2020, observations showed that the object remained active.
It was then ruled out that it was an active asteroid because it is extremely rare, but what about an active Jupiter Trojan? It would be unprecedented. Its location with the gas giant offered more clues. Jupiter has two massive swarms of asteroids along its orbital path, one in front and one behind. 2019 LD2 is in the group of Trojans ahead of the planet.
A fact that has puzzled scientists because, as they explain in their discovery, Trojan asteroids, due to their extreme age, should have dirty surfaces of volatile materials like water ice, and they should be dead.
Thus, the discovery of a lone active Trojan suggests that something else might be happening, perhaps the sudden exposure of deeper materials to the surface. As Lan Fitzsimmons, a professor of astronomy at Queen’s Belfast University who has been studying 2019 LD2, explained in a statement:
We have believed for decades that Trojan asteroids should have large amounts of ice underneath their surfaces, but we never had any evidence until now. ATLAS has shown that predictions of its icy nature can be correct.
An exciting object that will continue to be studied. In fact, NASA will launch the Lucy probe to visit Trojan asteroids. The spacecraft will investigate half a dozen of them between 2027 and 2033 and hopefully shed new light on these mysterious objects and how they were found around Jupiter.