Research box title
After traveling several billion miles towards the sun, a quirky young comet-like object orbiting between the giant planets has found a temporary parking space along the way. The object has perched near a family of captured ancient asteroids called Trojans, orbiting the sun next to Jupiter. This is the first time a comet-like object has been seen near the Trojan population.
The unexpected visitor belongs to a class of icy bodies found in the space between Jupiter and Neptune. Called ‘Centaurs’, they become active for the first time when heated as they approach the sun, dynamically transitioning into a more comet-like appearance.
Snapshots of visible light from NASA’s Hubble Space Telescope show that the vagabond object shows signs of comet activity, such as a tail gassing out in the form of jets, and an enveloping coma of dust and gas. Previous observations by NASA’s Spitzer Space Telescope provided clues about the composition of the comet-like object and the gases that drive its activity.
“Only Hubble was able to detect active comet-like features so far away with such high details, and the images clearly show these features, such as a roughly 400,000-mile wide tail and high-resolution features near the core due to a coma and jets,” said lead researcher Hubble Bryce Bolin of Caltech in Pasadena, California.
Bolin described the capture of the Centaur as a rare occurrence, adding, “The visitor had to have entered Jupiter’s orbit at just the right orbit to have such a configuration that it appears to be sharing its orbit with the Jupiter. planet. reexamine how it was captured by Jupiter and ended up among the Trojans. But we think it may be related to it having a somewhat close encounter with Jupiter. “
The team’s paper appears in the Feb. 11, 2021 issue of The Astronomical Journal.
The research team’s computer simulations show that the icy object, dubbed P / 2019 LD2 (LD2), likely swung close to Jupiter about two years ago. The planet then gravitated the wayward visitor to the co-orbital location of the Trojan asteroid group, which was about 437 million miles ahead of Jupiter.
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 on the extinct volcanoes, one on Mauna Kea and one on Haleakala. Japanese amateur astronomer Seiichi Yoshida gave the Hubble team a tip about possible comet activity. The astronomers then scanned archival data from the Zwicky Transient Facility, a large-scale survey conducted at Palomar Observatory in California, and realized that the object was clearly active in images as of April 2019.
They followed sightings from the Apache Point Observatory in New Mexico, which also pointed to the activity. The team observed the comet with Spitzer a few days before the observatory’s retirement in January 2020, and identified gas and dust around the comet’s nucleus. These observations convinced the team to use Hubble to take a closer look. Using Hubble’s sharp vision, the researchers identified the tail, the coma structure, the size of the dust particles and their ejection speed. These images helped confirm that the features are due to relatively new comet-like activity.
While LD2’s location is surprising, Bolin wonders if this pit stop could be a common release for some Sun-facing comets. “This could be part of the way from our solar system through the Jupiter Trojans to the inner solar system,” he said.
The unexpected guest is unlikely to stay between the asteroids for long. Computer simulations show that it will have another close encounter with Jupiter in about two years. The massive planet will boot the comet out of the system and continue its journey to the inner solar system.
“The cool thing is, you actually catch Jupiter as it orbits this object and change its orbital behavior and bring it into the inner system,” said team member Carey Lisse of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. . “Jupiter controls what happens to comets once they enter the inner system by changing their orbits.”
The icy invader is most likely one of the newest members of the so-called “bucket brigade” of comets to be thrown from its icy home in the Kuiper Belt and into the region of the giant planet through interactions with another Kuiper Belt object. Located outside Neptune’s orbit, the Kuiper Belt is an oasis of icy, leftover debris from the construction of our planets 4.6 billion years ago, containing millions of objects, and occasionally these objects have near misses or collisions that their orbits from the Kuiper Belt inward drastically change in the area of the giant planet.
The bucket brigade of icy relics endures a bumpy ride on their journey to the sun. They bounce gravity from one outer planet to the next in a game of celestial pinball before reaching the inner solar system and heating up as they get closer to the sun. The researchers say the objects spend as much or even more time around the gigantic planets, which pull on them by gravity – about 5 million years – than they enter the inner system where we live.
‘Inner system, comets with a short period disintegrate about once every century’, Lisse explains. “So in order to maintain the number of local comets we see today, we think the Bucket Brigade should deliver a new short-period comet about once every 100 years.”
An early bloomer
It surprised the researchers to see the outgassing activity on a comet 465 million miles away from the sun (where the intensity of the sunlight is 1 / 25th as strong as on Earth). “We were intrigued to see that the comet just got active for the first time, so far away from the sun, at distances where water ice is barely starting to sublimate,” said Bolin.
Water stays frozen on a comet until it’s about 200 million miles from the sun, where heat from sunlight converts water ice into gas escaping from the core in the form of rays. Thus, the activity indicates that the tail may not be made of water. Observations by Spitzer even pointed to the presence of carbon monoxide and carbon dioxide gas, which could power the creation of the comet’s tail and jets around Jupiter. These volatiles don’t need a lot of sunlight to heat their frozen form and convert it to gas.
Once the comet is kicked out of Jupiter’s orbit and continues its journey, it will be able to meet the giant planet again. “Short period comets like LD2 suffer their fate by being thrown into the sun and completely disintegrating, hitting a planet or getting too close to Jupiter again and thrown out of the solar system, which is the usual fate” , said Lisse. “Simulations show that in about 500,000 years there is a 90% chance that this object will be thrown out of the solar system and become an interstellar comet.”
The Hubble Space Telescope is a project of international collaboration between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland operates the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland conducts Hubble science operations. STScI is administered for NASA by the Association of Universities for Research in Astronomy, in Washington, DC NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, managed the Spitzer mission for NASA’s Science Mission Directorate in Washington, DC There scientific operations were conducted at the Spitzer Science Center at IPAC at Caltech. Spitzer’s full science catalog is available through the Spitzer Data Archive, housed in the Infrared Science Archive at IPAC. Spacecraft operations were based at Lockheed Martin Space in Littleton, Colorado.