A newly discovered asteroid, unlike any we’ve seen before, has been reported by scientists at the University of Hawaii. Dubbed 2019 LD2, it is unique not just because of what it is, but where – sharing an orbit with Jupiter.
Asteroids that behave like comets, emitting gas or sublimating, are rare but not unknown, and are called active asteroids.
However, 2019 LD2 boasts an asteroidal orbit but a comet-like tail, and is part of an asteroid swarm consisting of thousands of space rocks, known as the Jupiter Trojans, which orbit the gas giant in two groups.
One of the asteroid packs – which contains LD2 – orbits in front of Jupiter from our perspective, and the other behind the gas giant.
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. Given this estimated age, the ice on board any of the Jupiter Trojans would have sublimated long ago, puzzling researchers who spotted LD2 using the University of Hawaii’s Asteroid Terrestrial-impact Last Alert System (ATLAS) in June 2019. ATLAS’s main function is to scan the skies for any asteroids that could prove hazardous to Earth.
LD2’s comet-like elements were corroborated by the Las Cumbres Observatory, which found the same features in the following days.
“We have believed for decades that Trojan asteroids should have large amounts of ice beneath their surfaces, but never had any evidence until now,” said project collaborator and astronomer Alan Fitzsimmons of Queen’s University Belfast in Northern Ireland.
“ATLAS has shown that the predictions of their icy nature may well be correct.”
The current working theories for the formation of LD2’s ‘tail’ are that it suffered a recent collision with another space rock which may have caused it to start ‘bleeding’ ice from its core, or that it was only recently snared by the planet’s immense gravity.
NASA will launch its new spacecraft Lucy next year, with its 12-year mission to include visiting the Jupiter Trojans.
“Even though the ATLAS system is designed to search for dangerous asteroids, [it]sees other rare phenomena in our solar system and beyond while scanning the sky,” said ATLAS project principal investigator Larry Denneau.
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