Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Astronomy

Supervisor

Peter Brown

Abstract

Comets are thought to be responsible for the terrestrial accretion of water and organic materials. Comets evolve very quickly, and will generally deplete their volatiles in a few hundred revolutions. This process, or the aging of comets, is one of the most critical yet poorly understood problems in planetary astronomy. The goal of this thesis is to better understand this problem by examining different parts of the cometary aging spectrum of Jupiter-family comets (JFCs), a group of comets that dominates the cometary influx in the near-Earth space, using both telescopic and meteor observations. We examine two representative JFCs and the population of dormant comets. At the younger end of the aging spectrum, we examine a moderately active JFC, 15P/Finlay, and review the puzzle of the non-detection of the associated Finlayid meteor shower. We find that, although having been behaving like a dying comet in the past several 10 2 years, 15P/Finlay have produced energetic cometary outbursts without a clear reason. Towards the more aged end of the spectrum, we examine a weakly active JFC, 209P/LINEAR. By bridging telescopic observations at visible and infrared wavelength, meteor observations and dynamical investigations, we find that 209P/LINEAR is indeed likely an aged yet long-lived comet. At the other end of the spectrum, we examine the population of dormant near-Earth comets, by conducting a comprehensive meteor-based survey looking for dormant comets that have recently been active. We find the lower limit of the dormant comet fraction in the near-Earth object (NEO) population to be 2.0 ± 1.7%. This number is at the lower end of the numbers found using dynamical and telescopic techniques, which may imply that a significant fraction of comets in the true JFC population are weakly active and are not yet detected. These results have revealed interesting diversity in dying or dead comets, both in their behavior as well as their nature. An immediate quest in the understanding of cometary aging would be to examine a large number of dying or dead comets and understand their general characteristics.

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