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Monitoring the activity of distant comets

Presentation #101.06 in the session Cometary Volatiles.

Published onOct 20, 2022
Monitoring the activity of distant comets

Comets are remnants of planet formation, spending most of their lifetime relatively unchanged in the outer Solar System. Dynamically new comets (DNCs) are comets with nearly parabolic orbits suggesting they are entering the inner Solar System for the first time. DNCs are thought to have experienced minimal solar heating before detection and are therefore useful probes for relating observable cometary features to conditions in the pre-solar nebula and subsequent evolution. However, the mechanisms behind cometary activity at large distances are not well understood. Surveys today (e.g., Pan-STARRS, ATLAS) can discover comets at further distances from the Sun than ever before, allowing for more distant and longer baseline observations compared to DNC studies conducted in the past.

We have begun monitoring more than 25 long-period comets (LPCs) discovered inbound beyond 5 au using a network of telescopes through our Las Cumbres Observatory (LCO) Outbursting Objects Key (LOOK) project since August 2020 (Lister et al. 2022), and six LPCs inbound beyond 10 au using the SOAR telescope since February 2021. The 1-m telescopes of LCO observe the brighter objects at cadences of a few days, while the 4.1-m SOAR observes the fainter, more distant targets approximately monthly. We also utilize the 4.3-m Lowell Discovery Telescope (LDT) to complement SOAR observations in the northern hemisphere, and the 8.3-m Very Large Telescope (VLT) has been used to assess coma morphology. By monitoring the brightness evolution, colors, and coma morphology of distant comets over a range of heliocentric distances, we will better understand the behavior of comets at distances beyond which water sublimation is expected to be the driver of activity, make better predictions of brightness behavior of future discoveries, and assess whether brightness behavior can be used as a discriminator of dynamical age. We will present our ongoing results including comparisons between the brightness behavior of “new” vs returning comets, as well as instances of stalling, disintegration, color changes, and outbursts, particularly highlighting the distant outbursts of large comet C/2014 UN271 (Kelley et al. 2022).

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