Comets, unseen planets, and the outer fringes of the solar system

Comets have inspired awe since pre-historic times, but the modern study of comets only began with Halley's successful prediction of the return of what is now called Halley's comet. Even today there are only a few thousand comets with well-determined orbits.Nevertheless, the analysis of these orbits yields a compelling model for the formation, evolution and present distribution of comets. This model implies that there are two distinct sources of comets: the Oort cloud, containing over 100 billion comets at 5,000 to 50,000 times the Earth-Sun distance; and the Kuiper belt outside Neptune's orbit. I will review our current understanding of the formation of the Oort cloud and Kuiper belt, and what they can tell us about possible undiscovered planets beyond Neptune. If time permits, I'll describe some of the puzzles arising from the recent discovery of an interstellar asteroid/comet, ʻOumuamua.

Scott Tremaine
Institute for Advanced Study, Princeton
KIAA-PKU Auditorium
Qingjuan Yu
Tuesday, October 9, 2018 - 4:00pm to 5:00pm