Rotation of Comet Hartley 2 from Structures in the Coma

TL;DR

This study analyzes the CN coma structures of comet 103P/Hartley 2 over twenty nights, revealing a dynamically excited nucleus with a changing rotation rate, providing insights into its interior structure.

Contribution

It presents ground-based observations of the comet's coma to understand its unique rotational dynamics and interior constraints, complementing space mission data.

Findings

The comet's nucleus exhibits a changing rotational rate.

The nucleus shows no signs of rotational damping.

Constraints on the interior structure are derived from observed rotational behavior.

Abstract

The CN coma structure of the EPOXI mission target, comet 103P/Hartley 2, was observed during twenty nights from September to December 2010. These CN images probe the rotational state of the comet's nucleus and provide a ground-based observational context to complement the EPOXI observations. A dynamically excited cometary nucleus with a changing rotational rate is observed, a characteristic not seen in any comet in the past. The lack of rotational damping during the four-month observing interval places constraints on the interior structure of the nucleus.