Searching for early cometary activity and its evolution based on archival data

Comets are among the most ancient celestial bodies in the Solar System and play a pivotal role in our understanding of its formation and evolution, as well as the origin of life on Earth. As comets approach the Sun, they become active, releasing gas and dust that form the distinctive comae and tails observed in these celestial objects. Despite the extensive research conducted on cometary activity in closer proximity to the Sun, our understanding of its initiation and behavior at greater heliocentric distances remains limited. The primary objective of our research is to undertake a comprehensive investigation into the initial phases of cometary activity that transpire at considerable distances from the Sun. This investigation will encompass the examination of the manner in which this activity undergoes modification as comets draw near or retreat from the Sun. We have used archival data from a variety of observing programs, including, but not limited to, ZTF, Pan-STARRS, DES, ATLAS, and other relevant sources. It is asserted that these data will form the foundation for the development of more accurate models of cometary activity. The project focuses on the dust component of comets, their morphological features, and the dynamics of their interaction with solar radiation. The study will enhance our understanding of comet composition and the processes driving early activity by monitoring at different heliocentric distances, assessing dust formation, and observing color changes. The project is of paramount importance for preparing for data analysis from future missions, including the Comet Interceptor, which will study long-period comets, and observations from the recently commissioned Vera C. Rubin Observatory.

To start with, we chose the "blue" comet C/2016 R2 (PANSTARRS). We analyzed observations of it from the Skalnaté Pleso Observatory in January 2018, and from the ZTF archive, which contains observations from April and late 2018, as well as the entire year of 2019. In 2020 and 2021, the comet was so faint that we did not use the observations. ZTF observation measurements (primarily in the g and r filters; the i filter is minimally represented) show a very slight decrease in brightness with increasing geocentric and heliocentric distance. However, the Afρ parameter values (at an aperture of ~10,000 km) are practically constant (between 400 and 500 cm, depending on the filter) and have even been rising slightly since mid-2019.