Will Comet ISON (C/2012 S1) Survive Perihelion?

TL;DR

This study uses numerical simulations and historical data to assess whether Comet ISON will survive its close perihelion passage near the Sun, considering factors like size, density, and rotation.

Contribution

It provides new insights into the physical conditions affecting comet disruption, especially for ISON's specific perihelion distance and properties.

Findings

Disruption unlikely unless ISON's density is very low or it experiences significant spin-up.

Comet sizes below ~200 m are prone to sublimation-driven destruction.

Tidal disruption depends on density, rotation, and elongation, but is generally unlikely for ISON.

Abstract

On 2013 November 28 Comet ISON (C/2012 S1) will pass by the Sun with a perihelion distance of 2.7 solar radii. Understanding the possible outcomes for the comet's response to such a close passage by the Sun is important for planning observational campaigns and for inferring ISON's physical properties. We present new numerical simulations and interpret them in context with the historical track record of comet disruptions and of sungrazing comet behavior. Historical data suggest that sizes below ~200 m are susceptible to destruction by sublimation driven mass loss, while we find that for ISON's perihelion distance, densities lower than 0.1 g cm^-3 are required to tidally disrupt a retrograde or non-spinning body. Such low densities are substantially below the range of the best-determined comet nucleus densities, though dynamically new comets such as ISON have few measurements of physical properties. Disruption may occur for prograde rotation at densities up to 0.7 g cm^-3, with the chances of disruption increasing for lower density, faster prograde rotation, and increasing elongation of the nucleus. Given current constraints on ISON's nucleus properties and the typically determined values for these properties among all comets, we find tidal disruption to be unlikely unless other factors (e.g., spin-up via torquing) affect ISON substantially. Whether or not disruption occurs, the largest remnant must be big enough to survive subsequent mass loss due to sublimation in order for ISON to remain a viable comet well after perihelion.