Presentation #208.01D in the session “Observations of Short Period Comets”.
In my PhD thesis, I investigate the nature of two small body populations; the irregular satellite (“isat”) populations of the giant planets and the properties of fragmented nuclei of comets. In both cases the objective is to understand evolutionary processes acting on primitive solar system objects. An optical color survey of 43 irregular satellites enabled color comparisons with other small body populations that may reflect upon the origin of the isats. Ultrared matter (color index B–R ≥ 1.6), while abundant in the excited Kuiper belt and Centaur populations, is depleted from the isats (Fig. 1). Also, Figure (1) shows that the color distributions of the isats at each giant planet are statistically similar to each other, consistent with a common source region and/or evolutionary mechanism. Separately, the current observed supply of comets allows for estimates on the masses of their outer Solar System source regions, however, comet fragmentation may occur more often than previously thought, which will lead to shorter estimates of comet lifetimes than predicted. I analyzed comet 73P/Schwassmann-Wachmann 3 (73P) as a fragmented comet case study. Using archival Hubble Space Telescope (HST) data taken in 2006, about 120 images reveal the properties of the fragments of 73P and provide insight on its fragmentation mechanism. The measured rotation period of the nucleus is much longer than the critical period for rotational instability for any reasonable nucleus density and shape, even in the absence of tensile strength. The data also show hundreds of fragments within 73P-B and 73P-G, as seen in Figure (2), on which photometry is used to measure the brightness distribution of the fragments. I also measure the motion of these fragments and find the relative speeds of the fragments within 73P-B are a few m/s, implying an impulsive break-up about 11 days prior to the observations. Both the irregular satellites and comets are small bodies comprised of primitive material. The origin and evolution of the small bodies describe the early formation and evolution of the solar system itself.