Abstract: Schwamb

The Solar System Beyond Sedna

Dr. Meg Schwamb – Yale University

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. Some other mechanism no longer active in the solar system today is required to emplace Sedna on its orbit. Several possible scenarios have been offered to explain Sedna’s extreme orbit, including interactions with planet-sized bodies, stellar encounters, multiple stellar fly-bys in a stellar birth cluster, interstellar capture, and perturbations from a wide-binary solar companion. Each of the proposed scenarios offered to explain Sedna’s origin leaves a distinctive imprint on the members of this distant population. These planetesimals in the Sedna region are dynamically frozen and the relics of their formation process. Finding just a handful of these bodies, we can begin to read this dynamical record.

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 survey ~12,000 square degrees within ± 30 degrees of the ecliptic to a limiting R magnitude of 21.3 using the QUEST camera on the 1.2-m Samuel Oschin Telescope. To search for the fainter more common members of this distant class of solar system bodies, we have performed an ultra-deep survey using the Subaru Prime Focus Camera on the 8.2-m Subaru telescope covering ~43 square degrees to a limiting R magnitude of ~25. We will present the results of these surveys.

We will 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 be 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.