Comet-like Centaur spotted by Hubble near Jupiter's Trojans

The NASA Hubble Space Telescope has spied a comet-like object known as a Centaur that has settled near a group of captured ancient asteroids called Trojans orbiting alongside Jupiter. NASA says this is the first time a comet-like object has been spotted near the ancient Trojan population. The Centaur name classifies icy bodies in the space between Jupiter and Neptune that become active for the first time when heated as they approach the sun.

After heating, Centaurs dynamically transition into being more comet-like. Hubble captured snapshots of the icy body using visible light, showing that it has comet-like activity, including a tail, outgassing in the form of jets, and an interesting coma of dust and gas. Earlier observations by the Spitzer Space Telescope sheds light on the composition of the object and the gases that drive its activity. Hubble researchers say the aging space telescope is the only tool that could have detected active comet-like features from so far away with such detail.

The Centaur has a 400,000 mile-long tail, and the images show high-resolution features near the nucleus, including a coma and jets. Researcher Bryce Bolin says that the capture of the Centaur in the area is a rare event. For the capture to happen, the object had to come into the orbit of Jupiter at the exact right trajectory to have a configuration with the appearance of sharing its orbit with the planet.

Scientists are currently investigating how it was captured by Jupiter and ended up among the Trojans. The theory, for now, is that it's related to the fact that the Centaur had a somewhat close encounter with Jupiter. The icy object has been named P/2019 LD2 (LD2) and probably passed close to Jupiter about two years ago. At that time, the planet would have gravitationally drawn the visitor to the Trojan asteroid group's co-orbital location, which leads Jupiter by about 437 million miles.

As its name implies, this particular Centaur was discovered in early June 2019 by the University of Hawaii's Asteroid Terrestrial-impact Last Alert System, or ATLAS, telescopes that are located on the extinct volcanoes of Mauna Kea and Haleakala. The object won't stay among the Trojan asteroids for long. Computer simulations show it will have another close encounter with Jupiter in about two years, where it will be ejected from the Jovian system.