Coma morphology and dust emission pattern of comet C/2020 F3 (NEOWISE)

TL;DR

This study analyzes the dust emission and coma morphology of comet C/2020 F3 (NEOWISE), estimating its rotation period, spin axis, and dust properties through imaging and modeling during its close approach.

Contribution

It provides the first detailed analysis of the coma morphology, dust emission pattern, and rotation characteristics of comet NEOWISE based on observational data.

Findings

Estimated dust ejection velocity of 1.11 km/s.

Derived rotation period of approximately 7.8 hours.

Identified dust size range from 0.80 to 800 micrometers.

Abstract

The recent close approach of comet C/2020 F3 (NEOWISE) allowed us to study the morphology of its inner coma. From the measurement of the dust ejection velocityon spiral structures expanding around the nucleus, we estimated a mean deprojectedexpansion velocity Vd= 1.11+/-0.08 km s^-1. Assuming that a new shell formed after every rotation of the comet, a rotation period of 7.8+/-0.2 hours was derived. The spin axis orientation was estimated at RA 210+/-10d, Dec. +3+/-10d. The comamorphology appears related to two strong, diametrically opposite emissions located at mid-latitudes on the nucleus. A qualitative modelling of the coma produced consistent results with a wide range of dust sizes (0.80 to 800 micro-m), with inversely correlated densities (0.003 to 3.0 g cm^-3). Images taken with Vj and r-Sloan filters showed a greater concentration of dust in the first two shells, and an increasing density of radicals emitting in the B and V band-passes from the third shell outwards. Striae-like structures in the tail suggest that dust particles have different sizes.