Rebel comet makes temporary stop near Jupiter’s asteroids

The comet comes from the cold and finds an off-piste on its journey to the sun

Long car trips can be tedious and boring. That’s why many travelers on the road interrupt their difficult journey by making stops along the way.

Astronomers have discovered that at least one traveling comet does the same. The capricious object made a temporary stop near the giant Jupiter. The frozen visitor has plenty of company: he has settled near the family of captured asteroids known as the Trojans that co-orbit the Sun alongside Jupiter.

This is the first time that a comet-like object has been spotted near the population of Trojan asteroids. The Hubble Space Telescope Observations reveal that the wanderer shows signs of transitioning from an icy asteroid-like body to an active comet, germinating a long tail, giving off jets of matter and enveloping itself in a coma of dust and gas.

The intruder came from the frigid outskirts of our solar system, a comet nesting site called the Kuiper Belt. This nomad was probably torn off by the powerful gravity of Jupiter after brushing against the giant planet.

Jupiter’s uninvited guest is unlikely to stay on the planet for very long. As the “bouncer” of the solar system, the monster planet’s gravitational tugboat will ultimately reset the comet for its road trip to our Sun.

For the first time, a capricious, comet-like object has been spotted near the ancient asteroid family.

After traveling several billion kilometers towards the Sun, a capricious young object resembling a comet orbiting the giant planets has found a temporary parking space along the way. The object settled near a family of ancient captured asteroids, called Trojans, which orbit the Sun alongside Jupiter. This is the first time that a comet-like object has been spotted near the population of Trojans.

The unexpected visitor belongs to a class of icy bodies found in space between Jupiter and Neptune. Called Centaurs, they first become active when heated as the Sun approaches and dynamically transform to become more comet-like.

Snapshots of light visible through NASAThe Hubble Space Telescope reveals that the wandering object is showing signs of comet activity, such as a tail, outgassing in the form of jets, and an enveloping coma of dust and gas. Previous observations from NASA’s Spitzer Space Telescope have given clues to the composition of the comet-shaped object and the gases that direct its activity.

“Only Hubble could detect active comet-like features this far in such high detail, and the images clearly show these features, such as a broad tail about 400,000 miles long and high-resolution features near the nucleus in due to a coma and jets, ”said Bryce Bolin, senior researcher at Hubble, of Caltech in Pasadena, Calif.

Describing the capture of the Centaur as a rare event, Bolin added, “The visitor had to have come into Jupiter’s orbit just on the correct trajectory to have this type of configuration which makes it appear to share its orbit with the planet. . We are studying how he was captured by Jupiter and landed among the Trojans. But we think it could be related to the fact that he had a fairly close encounter with Jupiter.

The team’s article appears in the February 11, 2021 issue of The astronomical journal.

The research team’s computer simulations show that the icy object, called P / 2019 LD2 (LD2), likely flipped near Jupiter about two years ago. The planet then gravitated the lost visitor back to the co-orbital position of the Trojan asteroid cluster, leading Jupiter about 437 million miles.

Bucket Brigade

The nomadic object was discovered in early June 2019 by the University of Hawaii’s Asteroid Terrestrial-Impact Last Alert System (ATLAS) telescopes located on extinct volcanoes, one on Mauna Kea and one on Haleakala. Japanese amateur astronomer Seiichi Yoshida informed the Hubble team of possible comet activity. Astronomers then scanned archival data from the Zwicky Transitional Facility, a wide-field survey conducted at the Palomar Observatory in California, and realized that the object was clearly active in the April footage. 2019.

They followed up with sightings from the Apache Point Observatory in New Mexico, which also hinted at the activity. The team observed the comet using Spitzer just days before the observatory’s retreat in January 2020 and identified gas and dust around the comet’s nucleus. These observations convinced the team to use Hubble for a closer look. Aided by Hubble’s sharp vision, the researchers identified the tail, the structure of the coma, the size of the dust particles and their ejection speed. These images helped them confirm that the features are due to relatively new comet-like activity.

While the location of LD2 is surprising, Bolin wonders if this pit stop could be a common draw for some sun-facing comets. “It could be part of our solar system’s path through Jupiter’s Trojans to the inner solar system,” he said.

The unexpected guest probably won’t stay among the asteroids for very long. Computer simulations show he will have another close encounter with Jupiter in about two years. The large planet will ignite the system’s comet and continue its journey into the inner solar system.

“What’s cool is that you actually catch Jupiter throwing this object and changing its orbital behavior and bringing it into the internal system,” said Carey Lisse, a member of the Lab team. of Applied Physics (APL) from Johns Hopkins University in Laurel, Maryland. . “Jupiter controls what happens with comets once they enter the internal system by changing their orbits.”

The Icy Intruder is probably one of the last members of the so-called “bucket brigade” of comets to be kicked out of his icy home in the Kuiper Belt and Giant Planet region through interactions. with another Kuiper Belt object. Located beyond the orbit of Neptune, the Kuiper Belt is a haven of icy and leftover debris from the construction of our planets 4.6 billion years ago, containing millions of objects, and sometimes these objects have near misses or collisions that drastically change their orbits from the Kuiper belt inward. in the region of the giant planet.

The Frozen Relic Bucket Brigade endures a bumpy ride on their journey to the sun. They gravitationally bounce from one outer planet to another in a celestial pinball game before reaching the inner solar system, heating up as they approach the Sun. Researchers say objects spend as much time, if not more, around giant planets, which pull them gravitationally – about 5 million years ago – as they do through the internal system in which we live.

“The ‘short period’ comets in the internal system disintegrate about once a century,” Lisse explains. “So in order to maintain the number of local comets that we see today, we believe the Bucket Brigade needs to deliver a new short-lived comet about once every 100 years.”

An Early Bloomer

Seeing outgassing activity on a comet 465 million kilometers from the Sun (where the intensity of sunlight is 1 / 25th as strong as on Earth) surprised the researchers. “We were intrigued to see that the comet had just started to become active for the first time so far from the Sun at distances where the water ice is just starting to sublimate,” Bolin said.

Water remains frozen on a comet until it reaches about 200 million kilometers from the Sun, where the heat from sunlight converts water ice into gas that escapes from the core in the form of jets. . Thus, the activity indicates that the tail may not be made of water. In fact, Spitzer’s observations indicated the presence of carbon monoxide and carbon dioxide, which could be behind the creation of the tail and jets seen on the comet orbiting Jupiter. These birds do not need a lot of sunlight to heat their frozen form and convert them to gas.

Once the comet is expelled from Jupiter’s orbit and continues its journey, it may encounter the giant planet again. “Short period comets like LD2 meet their fate by being thrown into the Sun and totally disintegrating, hitting a planet or again venturing too close to Jupiter and being kicked out of the solar system, which is the usual fate, ”Lisse said. “The simulations show that in about 500,000 years, there is a 90% chance that this object will be ejected from the solar system and become an interstellar comet.”

Reference: “Initial characterization of the active centaur in transition, P / 2019 LD₂ (ATLAS), Using Hubble, Spitzer, ZTF, Keck, Apache Point Observatory, and GROWTH Visible and Infrared Imaging and Spectroscopy ”by Bryce T. Bolin, Yanga R. Fernandez, Carey M. Lisse, Timothy R. Holt, Zhong-Yi Lin, Josiah N. Purdum, Kunal P. Deshmukh, James M. Bauer, Eric C. Bellm, Dennis Bodewits, Kevin B. Burdge, Sean J. Carey, Chris M. Copperwheat, George Helou, Anna YQ Ho, Jonathan Horner, Jan van Roestel, Varun Bhalerao, Chan-Kao Chang, Christine Chen, Chen-Yen Hsu, Wing-Huen Ip, Mansi M. Kasliwal, Frank J. Masci, Chow-Choong Ngeow, Robert Quimby, Rick Burruss, Michael Coughlin, Richard Dekany, Alexandre Delacroix, Andrew Drake, Dmitry A. Duev, Matthew Graham, David Hale, Thomas Kupfer, Russ R. Laher, Ashish Mahabal, Przemyslaw J.Mróz, James D. Neill, Reed Riddle, Hector Rodriguez, Roger M. Smith , Maayane T. Soumagnac, Richard Walters, Lin Yan and Jeffry Zolkower, February 11, 2021, The astronomical journal.
DOI: 10.3847 / 1538-3881 / abd94b

The Hubble Space Telescope is an international cooperation project between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts science operations at Hubble. STScI is operated for NASA by the Association of Universities for Astronomical Research, Washington, DC NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, Calif., Managed the Spitzer mission for the Directorate of Missions NASA scientists in Washington, DC Science operations were conducted at IPAC’s Spitzer Science Center in Caltech. The entire Spitzer Science Catalog is available through the Spitzer Data Archive, hosted in the IPAC Infrared Science Archives. The spacecraft’s operations were based at Lockheed Martin Space in Littleton, Colorado.