Like many, I have been looking forward to and planning observations of the potential bright naked eye comet TSUCHINSHAN-ATLAS (C/2023 A3).
This paper contains some interesting thoughts by Dr. Zdenek Sekanina (formerly at NASA/JPL, and an expert on split and dissolving comets) regarding being cautious about brightness predictions for comet C/2023 A3. The paper analyses recent observations and predicts that the comet is in advanced stages of breaking up and will disintegrate completely before perihelion.
INEVITABLE ENDGAME OF COMET TSUCHINSHAN-ATLAS (C/2023 A3)
Zdenek Sekanina
La Canada Flintridge, California 91011, U.S.A.;
ZdenSek@gmail.com
Version July 9, 2024
Full paper:
https://arxiv.org/pdf/2407.06166?fbclid ... J1DiFZBgQ
ABSTRACT
Hopes are being widely expressed that C/2023 A3 could become a naked-eye object about the time of its perihelion passage in late 2024. However, based on its past and current performance, the comet is expected to disintegrate before reaching perihelion. Independent lines of evidence point to its forthcoming inevitable collapse.
The first issue, which was recently called attention to by I. Ferrin, is this Oort cloud comet’s failure to brighten at a heliocentric distance exceeding 2 AU, about 160 days preperihelion, accompanied by a sharp drop in the production of dust (Afρ). Apparent over a longer period of time, but largely ignored, has been the barycentric original semimajor axis inching toward negative numbers and the mean residual increasing after the light-curve anomaly, suggesting a fragmented nucleus whose motion is being affected by a nongravitational acceleration; and an unusually narrow, teardrop dust tail with its peculiar orientation, implying copious emission of large grains far from the Sun but no microscopic dust recently.
This evidence suggests that the comet has entered an advanced phase of fragmentation, in which increasing numbers of dry, fractured refractory solids stay assembled in dark, porous blobs of exotic shape, becoming undetectable as they gradually disperse in space.
If correct, this is disappointing news.
Joe Cali
