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We present preliminary results from an observational and thermo-dynamical study of 77 Centaurs aimed at identifying and characterizing active objects in the giant planet region. Centaurs are small bodies orbiting between Jupiter and Neptune which were scattered inwards from their source populations in the Scattering disc. About 5% of the population displays comet-like activity during their transition through the solar system, the source and triggers of which are not well understood. The range of heliocentric distances where the active Centaurs have been observed, and their median lifetime of ~1 Myr in the region, suggest this activity is neither driven by water-ice sublimation, nor entirely by super-volatiles.
Our snapshot observations carried between 2017 and 2021 yielded only one active Centaur in our sample - 2014 OG392, and further confirmed a hypothesized distance limit of ~14au, beyond which there are no active Centaurs known, despite activity being observed in comets much further in the Solar system. Our thermodynamical analysis suggests that a favorable orbit and volatile content might not be enough for a Centaur to activate, and a certain trigger might be needed. Our further dynamical study allowed us to identify a common feature in the past orbital evolution of all known active Centaurs - a recent dramatic change of semi-major axis which could act as an activity trigger. This feature is missing in the recent history of known inactive Centaurs, and we speculate such rapid orbital changes might be used to identify candidates for future outbursts. |