Planetary and exoplanetary Astronomy Lunch Seminar (PALS) for 2021-10-18

Series: Planetary and exoplanetary Astronomy Lunch Seminar (PALS)
Date: Monday 18-Oct-2021
Time: 11:15-12:15
Location: Online via Zoom (link sent out to the PALS distribution list prior to the talk)
Speaker: Yun Zhang (Observatoire de la Côte d’Azur)
Title: Internal properties and structural evolution of top-shaped asteroids as revealed by Bennu and Didymos

Most small bodies with sizes larger than tens of meters are made of numerous pieces of rocks and sometimes ices that have coalesced under the influence of gravity (so called “rubble piles”). As their own gravity is not enough to squeeze them into spheres, these small bodies exhibit a variety of shapes and surface morphologies, recording their life stories. Radar observations have shown that a large fraction of near-Earth asteroids have top-like shapes, which could be the outcome of the rotational reshaping of the so-called YORP effect. Most of top-shaped bodies are accompanied by a small satellite, such as the asteroid Didymos, while a few are alone, such as the asteroid Bennu and Ryugu. Here I will show how top-shaped bodies evolve in general under YORP based on our recent studies. By modeling rubble-pile structural dynamics using the soft-sphere discrete element method, we found that their structural evolution are very sensitive to their internal structure and material properties. The conditions allowing the formation of satellites by YORP-induced mass shedding and implications for Bennu and Didymos will be given.

For further information contact PALS coordinators Drs. Quanzhi Ye ( and Matej Malik (


Special accommodations for individuals with disabilities can be made by calling (301) 405-3001. It would be appreciated if we are notified at least one week in advance.


Directions and information about parking can be found here.

This page was automatically generated on: 11-Oct-2021.