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A celestial object found in 2021 in the asteroid belt has been confirmed to be a main belt comet, characterized by its icy composition and cometary behavior near the Sun. The researchers emphasize the importance of these findings for understanding the distribution of ice in the inner part of the Solar System.
Discovery of a new main belt comet
In 2021, scientists discovered a mysterious object in the main asteroid belt. So far, it has been identified as a main belt comet by Henry Hsieh of the Planetary Science Institute, Scott Sheppard of the Carnegie Institution for Science, and Audrey Thirouen of the Lowell Observatory.
Main belt comets are icy objects located in the asteroid belt between Mars and Jupiter. This is a surprising location, as icy bodies are usually found in the cold outer regions of the solar system. These comets have distinctive features such as tails trailing from the Sun or fuzzy clouds caused by the sun's heat vaporizing their ice. The first main belt comets were identified in 2006 by Hsieh and his Dr. David Jewitt of the University of Hawaii.
Characteristics and methods of observation
Main belt comets belong to a wider group of Solar System objects called active asteroids, which resemble comets but move in asteroid orbits in the warmer inner part of the Solar System. Active asteroids include not only objects with cometary behavior caused by evaporation of ice, but also those whose dust clouds and tails are the result of impacts or rapid rotation. Although main-belt comets and active asteroids remain relatively rare, as observational techniques improve, scientists are discovering them more frequently.
Xie and his colleagues observed the active asteroid 456P/PANSTARRS twice with the Magellan Baade Telescope and the Lowell Discovery Telescope in October 2024 to establish its status as the 14th confirmed main belt comet. They published their findings in Research Notes of the American Astronomical Society.
Definition of comet-like activity
"This object is not just an asteroid that experienced a one-off event that made it active once, but is an inherently active, icy body similar to other comets from the outer solar system," Xie said.
If the activity of 456P/PANSTARRS was due to something other than the evaporation of ice, then its tail should have appeared only once randomly, and not repeatedly when it was close to the Sun. On the other hand, an icy object heats up every time it approaches the Sun, and the evaporated ice drags dust with it. When the object moves away from the Sun and cools, the activity stops.
The importance of continuing research
Observations of repeated dust ejection activity during close approaches to the Sun are currently considered the best and most reliable way to identify main-belt comets.
"Very few confirmed main belt comets are known so far," Xie said. "We want to create a population so that we can get a clearer picture of their broader properties, such as their sizes, durations of activity and distribution, for example in the asteroid belt, so that they can be better used to trace the ice. in the solar system in general".
