At https://phys.org/news/2024-10-webb-telescope-unusual-gas-jets.html … centaur objects orbit the Sun between Jupiter and Neptune. NASAs James Webb Space Telescope has mapped gases spewing from Centaur 29P – suggesting a varied composition. Is it an asteroid or a giant comet?
These objects originally orbited beyond Neptune but have since become stuck in a more forward orbit between Jupiter and Neptune. They are now being held back from entry into the inner solar system – but now and again they can be deflected past Jupiter, it is thought. Bill Napier classifies them as giant comets – but not necessarily always acting like a comet. The Clube and Napier theory is based on the idea a giant comet squeezed past Jupiter and took a new, short period orbit in the inner solar system. Over thousands of years the centaur object broke up and was a danger to the inhabitants of the Earth.
Returning to the link we are told centaurs share many characteristics with short period comets – but why are they outgassing so far from the Sun. In fact, the reasons why Centaur 29P’s outbursts of brightness happen, and the mechanism behind it, astronomers intend to research further. They have already modelled the jets of what appears to be CO and CO2. However, the consensus view of comets is under strain as it is thought they are too cold for water ice to sublimate. In fact, the process of sublimation is itself up for grabs it might appear to a non specialist in the subject. So far, astronomers have just a snapshot in time of the jets – on a single occasion. They hope to return to the centaur in order to study it over a longer period. See https://doi.org/10.1038/s41550-024-02319-3 …
At https://phys.org/news/2024-09-asteroid-ceres-ocean-world-slowly.html … the asteroid Ceres once had a lot of water, it has been deduced. It is classified in the headline at the link as an ocean world that slowly formed into a giant, and murky, icy orb. It is crater rich – and lies between the orbits of Mars and Jupiter, the largest object in the asteroid belt. It has a diameter of 950 km.