The dynamics of comets, and modified gravity in the solar system

Event Date:
2025-02-03T16:00:00
2025-02-03T17:00:00
Event Location:
HENN 318 & simultaneously broadcast on zoom
Speaker:
Scott Tremaine, Institute for Advanced Study, Princeton University
Related Upcoming Events:
Astronomy Colloquia
Intended Audience:
Everyone
Local Contact:

Allison Man (aman@phas.ubc.ca) and Brett Gladman (gladman@astro.ubc.ca)

All are welcome to this event!

Event Information:

Abstract:

This talk has two (related) parts:

1. Comets have inspired awe since prehistoric times, but even today there are only a few thousand comets with well-determined orbits. Nevertheless, the analysis of this limited sample yields a compelling "standard model" for the formation, evolution and present distribution of comets. This model implies that the primary source of comets is the Oort cloud, containing over 100 billion comets at 5,000 to 100,000 times the Earth-Sun distance. I will review our current understanding of the history and structure of the Oort cloud.

2. The hypothesis that most of the matter in the universe is in some unknown dark form is fundamental to modern cosmology. A speculative alternative is that our understanding of the law of gravity is incomplete. The most influential theory of this kind is modified Newtonian dynamics (MOND), which postulates a breakdown of Newton's law of gravity below some critical acceleration threshold. We explore the predictions of the simplest version of MOND for the formation and evolution of the Oort cloud, and conclude that this is not the correct description of gravity.

Bio:

Scott Tremaine has made seminal contributions to understanding the formation and evolution of planetary systems, comets, black holes, star clusters, galaxies, and galaxy systems. He predicted the Kuiper belt of comets beyond Neptune and, with Peter Goldreich, the existence of shepherd satellites and density waves in Saturn’s ring system, as well as the phenomenon of planetary migration. He interpreted double-nuclei galaxies, such as the nearby Andromeda galaxy, as eccentric stellar disks, and elucidated the role of dynamical friction in galaxy evolution.

Learn More:

Add to Calendar 2025-02-03T16:00:00 2025-02-03T17:00:00 The dynamics of comets, and modified gravity in the solar system Event Information: Abstract: This talk has two (related) parts: 1. Comets have inspired awe since prehistoric times, but even today there are only a few thousand comets with well-determined orbits. Nevertheless, the analysis of this limited sample yields a compelling "standard model" for the formation, evolution and present distribution of comets. This model implies that the primary source of comets is the Oort cloud, containing over 100 billion comets at 5,000 to 100,000 times the Earth-Sun distance. I will review our current understanding of the history and structure of the Oort cloud. 2. The hypothesis that most of the matter in the universe is in some unknown dark form is fundamental to modern cosmology. A speculative alternative is that our understanding of the law of gravity is incomplete. The most influential theory of this kind is modified Newtonian dynamics (MOND), which postulates a breakdown of Newton's law of gravity below some critical acceleration threshold. We explore the predictions of the simplest version of MOND for the formation and evolution of the Oort cloud, and conclude that this is not the correct description of gravity. Bio: Scott Tremaine has made seminal contributions to understanding the formation and evolution of planetary systems, comets, black holes, star clusters, galaxies, and galaxy systems. He predicted the Kuiper belt of comets beyond Neptune and, with Peter Goldreich, the existence of shepherd satellites and density waves in Saturn’s ring system, as well as the phenomenon of planetary migration. He interpreted double-nuclei galaxies, such as the nearby Andromeda galaxy, as eccentric stellar disks, and elucidated the role of dynamical friction in galaxy evolution. Learn More: See his faculty page here: https://www.ias.edu/scholars/tremaine See his personal website here: https://www.ias.edu/sns/scott-tremaine Browse through his lectures: https://www.ias.edu/sns/tremaine/lectures More on MOND: https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics An introduction to comets: https://science.nasa.gov/solar-system/comets/ Oort Cloud: https://science.nasa.gov/solar-system/oort-cloud/  Event Location: HENN 318 & simultaneously broadcast on zoom