Astronomers have spotted a ''first-of-its-kind'' object near Jupiter's orbit, which appears to be a cross between an asteroid and a comet.
Researchers using the University of Hawaii’s Asteroid Terrestrial-impact Last Alert System (ATLAS) have found (via Gizmodo) a Trojan asteroid, 2019 LD2, that not only follows an odd orbit ahead of Jupiter but also sports an icy tail — it’s a unique “crossover” between asteroid and comet. It only appears to have been active for less than a year, too, which is unusual when Jupiter Trojans are often billions of years old and should have lost their ice a long time ago.
Trojan asteroids follow the same orbit as a planet, but stay either around 60 degrees ahead of or 60 degrees behind along the orbit. Earth has at least one Trojan asteroid, and Neptune has dozens. Jupiter has hundreds of thousands.
The Jupiter Trojan asteroids orbit the Sun in two huge swarms, one swarm orbiting ahead of the planet (where 2019 LD2 was found) and one swarm orbiting behind it.
The Trojan asteroids have been captured into these orbits by Jupiter's strong gravity. 2019 LD2 is ''first-of-its-kind'' because most Jupiter Trojans were captured billions of years ago.
ATLAS is a NASA-funded project using wide-field telescopes to rapidly scan the sky for asteroids that might pose an impact threat to Earth.