Trojan asteroids follow the same orbit as a planet but stay either around 60 degrees ahead of or 60 degrees behind along the orbit.
The rock was firstly detected last June when scientists from various universities throughout the world rushed to study ATLAS images of the unusual object, noting the "cometary" nature of the asteroid's body and observing its behaviour more closely. These objects initially appear to be asteroids, and later develop activity, such as tails, that are typical of comets.
A new kind of space rock that is a crossover between an asteroid and a comet - called an active asteroid - has been spotted sharing an orbit with Jupiter. Thus, the nature of 2019 LD2 remains obscure, as the object is either a recent Jovian acquisition or an old asteroid that has suffered some impact which provoked a release of ice buried under its surface. Dubbed 2019 LD2, it is unique not just because of what it is, but where - sharing an orbit with Jupiter.
2019 LD2 first caught astronomers' attention in early June of previous year, when the University of Hawaiʻi's Asteroid Terrestrial-impact Last Alert System (ATLAS) detected a faint new signal that appeared to be an asteroid in the Trojan group. Follow-up observations by UH astronomer J.D.
LD2's comet-like parts have been corroborated by the Las Cumbres Observatory, which discovered the identical options within the following days.
Next, in July 2019, ATLAS detected 2019 LD2 again with a clear view of the comet with a faint tail made of dust or gas. Those observations showed that 2019 LD2 has probably been continuously active for nearly a year. So, it's not the "what", but the "where" that makes 2019 LD2 special. One of it orbits in front of Jupiter, where 2019 LD2 is, and the other trails behind it, in curved areas concentrating on the planet's Lagrangian edges. And it's the first Jupiter Trojans astronomers have ever spotted discharging out gas like a comet.
The asteroid swarm is thought to have been pulled in by Jupiter around four billion years ago while the planets in our solar system were still finding their places.
But what if the ice is inside the asteroids?
"We have believed for decades that Trojan asteroids should have large amounts of ice beneath their surfaces, but never had any evidence until now".
"ATLAS has proven that the predictions of their icy nature could be right".
If 2019 LD2 had recently collided with another chunk of rock, the impact could have dislodged enough material to expose this previously sealed ice, allowing it to sublimate and outgas.
There are lots of asteroids in the Jupiter Trojan category, divided into two groups.
NASA will launch its new spacecraft Lucy subsequent 12 months, with its 12-year mission to incorporate visiting the Jupiter Trojans.
For example, if Earth passes through the tail of a comet, much of the debris burns up in the atmosphere, forming a meteor shower.