Beyond Sedna: Probing the Distant Solar System

Citation

Schwamb, Megan E. (2011) Beyond Sedna: Probing the Distant Solar System. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/W4B2-1B44. https://resolver.caltech.edu/CaltechTHESIS:07082010-134040468

Abstract

This thesis presents studies in observational planetary astronomy probing the structure of the Kuiper belt and beyond. The discovery of Sedna on a highly eccentric orbit beyond Neptune challenges our understanding of the solar system and suggests the presence of a population of icy bodies residing past the Kuiper belt. With a perihelion of 76 AU, Sedna is well beyond the reach of the gas-giants and could not be scattered onto its highly eccentric orbit from interactions with Neptune alone. Sedna’s aphelion at ∼1000 AU is too far from the edge of the solar system to feel the perturbing effects of passing stars or galactic tides in the present-day solar neighborhood. Sedna must have been emplaced in its orbit at an earlier time when massive unknown bodies were present in or near the solar system. The orbits of distant Sedna-like bodies are dynamically frozen and serve as the relics of their formation process.

We have performed two surveys to search for additional members of the Sedna population. In order to find the largest and brightest Sedna-like bodies we have searched ∼12,000 square degrees within +/- 30 degrees of the ecliptic to a limiting R magnitude of 21.3 using the QUEST camera on the 1.2m Samuel Oschin Telescope. To search for the fainter, more common members of this distant class of solar system bodies, we have performed an deep survey using the Subaru Prime Focus Camera on the 8.2m Subaru telescope covering 43 square degrees to a limiting R magnitude of 25.3. Searching over a two-night baseline, we were sensitive to motions out to distances of approximately 1000 AU.

We present the results of these surveys. We discuss the implications for a distant Sedna-like population beyond the Kuiper belt and discuss future prospects for detecting and studying these distant bodies, focusing in particular on the constraints we can place on the embedded stellar cluster environment the early Sun may have been born in, where the location and distribution of Sedna-like orbits sculpted by multiple stellar encounters is indicative of the birth cluster size. These surveys were specifically designed to find the select members of a distant Sedna population but were also sensitive to the dynamically excited off ecliptic populations of the Kuiper belt including the hot classicals, resonant, scattered disk, and detached Kuiper belt populations. We present our observed latitude distributions and implications for the plutino population.

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