After an unpredictable young comet-like object orbiting between the giant planets traveled several billion miles in the direction of the sun, it found a temporary parking space along the way. The object has taken up residence near a family of trapped ancient asteroids called Trojans, which orbit the Sun next to Jupiter. This is the first time a comet-like object has been detected near the Trojans.
Astronomers found a stray comet that paused before possibly continuing its journey. The headstrong object temporarily stopped near the giant Jupiter. The icy visitor has plenty of company. It has settled near the family of trapped asteroids known as Trojans, which orbit the Sun next to Jupiter. This is the first time a comet-like object has been discovered near the Trojan asteroid population. Observations from the Hubble Space Telescope show that the vagabond shows signs of transition from a cold, asteroid-like body to an active comet, sprouting a long tail, outgassing jets of material, and enveloping itself in a coma of dust and gas.Credit: NASA, ESA, and B. . Bolin (Caltech)
The unexpected visitor belongs to a class of icy bodies found in space between Jupiter and Neptune. Referred to as “centaurs,” they first become active when approaching the sun and dynamically become more comet-like.
Visible light snapshots from NASA’s Hubble Space Telescope show the wandering object showing signs of cometary activity, such as: B. a tail, outgassing 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 fuel its activity.
“Only Hubble could see active comet-like features that far away in such high detail, and the images clearly show those features, such as: B. A tail about 400,000 miles long and high resolution features near the core due to a coma and jet, ”said senior Hubble researcher Bryce Bolin of Caltech in Pasadena, California.
Describing the centaur’s capture as a rare occurrence, Bolin added, “The visitor had to have entered Jupiter’s orbit on exactly the right trajectory to get this type of configuration that appears to be its orbit with the planet to share. We investigate how it was captured by Jupiter and ended up among the Trojans. But we think it might be related to the fact that there was a pretty close encounter with Jupiter. “
The team’s paper appears in the February 11, 2021 issue of the Astronomical Journal.
The research team’s computer simulations show that the icy object P / 2019 LD2 (LD2) was likely swinging near Jupiter about two years ago. The planet then gravity nudged the headstrong visitor to the co-orbital position of the Trojan asteroid group and guided Jupiter approximately 437 million miles.
After an unpredictable young comet-like object orbiting between the giant planets traveled several billion miles in the direction of the sun, it found a temporary parking space along the way. The object has taken up residence near a family of trapped ancient asteroids called Trojans, which orbit the Sun next to Jupiter. This is the first time a comet-like object has been detected near the Trojans. Credits: NASA
The nomadic object was discovered in early June 2019 by the University of Hawaii ATLAS (Asteroid Terrestrial Impact Last Alert System) telescopes located on the extinct volcanoes, one on Mauna Kea and one on Haleakala. Japanese amateur astronomer Seiichi Yoshida alerted the Hubble team to possible cometary activity. The astronomers then scanned archival data from the Zwicky Transient Facility, a wide-field survey conducted at the Palomar Observatory in California, and found that the object was clearly active in images as of April 2019.
They followed with observations from the Apache Point Observatory in New Mexico, which also indicated the activity. The team observed the comet with Spitzer a few days before the observatory’s resignation in January 2020 and identified gas and dust around the comet’s core. These observations convinced the team to use Hubble to take a closer look. Using Hubble’s keen vision, the researchers identified the tail, the coma structure, the size of the dust particles and their ejection speed. These images helped them confirm that the features were due to relatively recent comet-like activity.
While LD2’s location is surprising, Bolin wonders if this pit stop could be a frequent deduction for some sun-bound comets. “This could be part of the way from our solar system via the Jupiter Trojans to the inner solar system,” he said.
The unexpected guest is unlikely to stay among the asteroids for long. Computer simulations show that there will be another close encounter with Jupiter in about two more years. The powerful planet will boot the comet from the system and continue its journey to the inner solar system.
“The cool thing is, you actually catch Jupiter spinning this object around, changing its orbital behavior, and bringing it into the inner system,” said team member Carey Lisse of the Applied Physics Laboratory (APL) at Johns Hopkins University in Laurel, Maryland. “Jupiter controls what happens to comets when they enter the internal system by changing their orbits.”
The icy intruder is most likely one of the youngest members of the so-called “bucket brigade” of comets thrown from their cold home in the Kuiper belt into the region of the giant planet through interactions with another Kuiper belt object. Located beyond Neptune’s orbit, the Kuiper Belt is an oasis of icy, leftover debris from the construction of our planets 4.6 billion years ago that contains millions of objects. Occasionally these objects have near misses or collisions that drastically change their orbits from the Kuiper Belt inward into the giant planet region.
The bucket brigade of icy relics endures a bumpy ride on their journey into the sun. They jump gravitationally from one outer planet to the next in a heavenly pinball game before reaching the inner solar system, and warm up as they approach the sun. The researchers say that the objects spend as much or even more time around the giant planets and gravitationally attract them – about 5 million years – than they get into the internal system in which we live.
“Inner system, ‘short-period’ comets break up about once a century,” Lisse explained. “To maintain the number of local comets we see today, the bucket brigade has to deliver a new short-term comet roughly every 100 years.”
An early bloomer
The researchers surprised the outgassing activity on a comet 465 million miles from the Sun (where the intensity of sunlight is 1/25 as strong as on Earth). “We were intrigued to see that the comet just became active for the first time this far from the Sun, at distances where the water ice barely begins to sublime,” said Bolin.
Water stays frozen on a comet until it is about 200 million miles from the Sun, where heat from sunlight converts water ice into gas, which escapes from the core in the form of jets. So the activity signals that the tail may not be made of water. In fact, observations by Spitzer suggested the presence of carbon monoxide and carbon dioxide gas, which could fuel the formation of the tail and jets on the Jupiter-orbiting comet. These volatiles don’t require much sunlight to heat their frozen form and turn it into gas.
As soon as the comet is thrown out of Jupiter’s orbit and continues its journey, it may hit the giant planet again. “Short-term comets like LD2 meet their fate by being thrown into the sun and completely disintegrating, hitting a planet or venturing too close to Jupiter again and being thrown out of the solar system, which is the usual fate,” Lisse said. “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.”
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 Hubble science operations. STScI is operated 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, directed the Spitzer Mission for NASA’s Science Mission Directorate in Washington, DC at the Spitzer Science Center at IPAC in Caltech. The entire Spitzer science catalog is available through the Spitzer data archive, which is located in the Infrared Science Archive of the IPAC. The spacecraft was operated at Lockheed Martin Space in Littleton, Colorado.
Credits: NASA, ESA and B. Bolin (Caltech)