Dust and Gas Characterization of the Great C/2023 A3 comet Near Perihelion

Comets are remnants of the early Solar System, serving as natural archives of refractory and volatile compounds that have not undergone significant alteration, offering valuable clues about its origins and the early solar system. In this work, we present a characterization of the dust and gas environment of the long-period comet C/2023 A3 (Tsuchinshan-ATLAS). It was discovered on January 9, 2023, by the Tsuchinshan Observatory in China and independently by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in South Africa. Comet C/2023 A3, also known as the “Great Comet of 2024”, was a highly anticipated bright comet that transited the inner Solar System in late 2024. The comet reached perihelion on September 27, 2024, at a distance of approximately 0.39 AU. Despite the close approach, the nucleus did not fragment, making it a primary target for assessing the primitive composition of the outer solar system.

We investigate Comet C/2023 A3 through the analysis of a comprehensive observational dataset, combining visible-range images and spectra, acquired during the pre- and post-perihelion passages in 2024. Observations were obtained using the 1.82-m Copernico Telescope and the 1.22-m Galileo Telescope at the Asiago Astrophysical Observatory. Additionally, the comet entered the field-of-view of the SOHO/LASCO C3 coronograph [1] from October 7 to 11, 2024, providing near-real-time images of its dust and ion tails. This dataset allowed for nearly continuous study of the dust and gas activity from 1.7 AU inbound to 1.8 AU outbound, encompassing the perihelion passage.

Preliminary spectroscopic analysis confirmed the presence of volatile species, including CO, CO2, and H2O, and indicated a CN depletion typical of Oort Cloud bodies. We also determined the Afρ parameter, obtaining a value of approximately 4000 cm, which confirms the high dust production rate previously reported for this comet [2,3,4,5].

Future analysis will include the calculation of gas production rates, the derivation of upper limits for the production rates of key molecular species, and a comparison of these results with those of other comets reported in the literature. We will also determine the Afρ parameter as a function of time, as well as the radial and azimuthal distributions of dust, to study any correlations among these parameters. The derived dust and gas results will be discussed in terms of both spatial distribution and temporal evolution.

These findings will contribute to a deeper understanding of the compositional diversity and evolutionary processes of this long-period comet, a body of particular interest as a possible target for the Comet Interceptor mission [6].

References

• [1] Brueckner, G. E., et al.1995. Solar Physics, 162, 357-402.
• [2]Cambianica et al. 2024, Planetary and Space Science, Volume 261, id.106102
• [4]Spiro et al. 2024 AAS Division for Planetary Sciences meeting #56, id. 401.07. Bulletin of the American Astronomical Society, Vol. 56, No. 8 e-id 2024n8i401p07
• [5] Moreno et al. 2025. Monthly Notices of the Royal Astronomical Society, Volume 539, Issue 2, pp. 949-955, 7 pp.    
• [6] Snodgrass and Jones, 2019 Nature Communications, Volume 10, id. 5418