For the first time ever, a comet has been witnessed near Jupiter’s ancient asteroids called Trojans that orbit the sun along with the Gas Giant. The young object, which has been named P/2019 LD2 (or LD2), belongs to a group of icy bodies called Centaurs that are located between Jupiter and Neptune. When Centaurs get closer to the sun, they heat up and become more like a comet.
LD2 is thought to be part of the “bucket brigade” of comets that have been kicked out of the Kuiper Belt by collisions with other objects and sent flying towards Jupiter.
The temporary visitor was witnessed by NASA’s Spitzer Space Telescope and then visible-light photos from the Hubble Space Telescope revealed that it had comet-like features like a tail. “Only Hubble could detect active comet-like features this far away at such high detail, and the images clearly show these features, such as a roughly 400,000-mile-long broad tail and high-resolution features near the nucleus due to a coma and jets,” explained Bryce Bolin who is the lead Hubble researcher at Caltech in Pasadena, California.
Image of P/2019 LD2 taken by the Hubble in April 2020.
The fact that the icy object has outgassing activity while situated 465 million miles away from the sun is quite surprising as Bolin stated, “We were intrigued to see that the comet had just started to become active for the first time so far away from the Sun at distances where water ice is barely starting to sublimate.” In fact, the water ice should only change into gas that ejects from the nucleus when the object is approximately 200 million miles from the sun. However, Spitzer’s observations did indicate that carbon monoxide and carbon dioxide gas were present in the tail, so that could explain it.
As for how it ended up near Jupiter’s Trojans, it is believed that LD2 got a little too close to Jupiter approximately two years ago and the Gas Giant’s gravitational pull ended up sending the icy object towards the Trojan asteroid group.
And it’ll probably only stay there for another couple of years. According to computer simulations, the icy object is expected to get close to Jupiter in another two years and that encounter should shove it on its way towards the inner solar system.
But it may not be all smooth sailing for LD2 after escaping Jupiter’s Trojans as Carey Lisse from the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, explained, “Short-period comets like LD2 meet their fate by being thrown into the Sun and totally disintegrating, hitting a planet, or venturing too close to Jupiter once again and getting thrown out of the solar system, which is the usual fate,” adding, “Simulations show that in about 500,000 years, there’s a 90% probability that this object will be ejected from the solar system and become an interstellar comet.”
Image of P/2019 LD2 taken by the Hubble in February 2021.
Lisse went on to say how incredible this event is, “The cool thing is that you’re actually catching Jupiter flinging this object around and changing its orbital behavior and bringing it into the inner system.” “Jupiter controls what’s going on with comets once they get into the inner system by altering their orbits.”
This event also raises the question of whether this has happened before but wasn’t documented by our telescopes. “This could be part of the pathway from our solar system through the Jupiter Trojans to the inner solar system,” Bolin noted.
The research was published in The Astronomical Journal where it can be read in full.
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