September 23, 2022
Colloquium Topic: The Solar System's Most Unusual Objects: The dynamics of inner-Venus and retrograde asteroids
The Solar System is often thought of as a static environment, in which the orbits of the planets, asteroids, and comets remain continuously unchanged. But although its current architecture has existed for nearly the past 4.5 billion years, the Solar System is far from the unvarying environment we often imagine. The gravitational influence of the planets over small bodies has modified many asteroid orbits in quite dramatic ways. This is particularly true for asteroids that reach the Solar System's innermost regions. These gravitational interactions can cause the nearly circular orbits of asteroids located in the main asteroid belt between Mars and Jupiter to become highly elliptical until they cross the orbits of the terrestrial planets, often bringing them into near-Earth space and eventually the near-Sun region. I will discuss how asteroids can move from the main asteroid belt to the Solar System's innermost region as well as the typical dynamical behavior and recent discoveries of asteroids that live very close to the Sun. I will also describe efforts being made to ensure the near-Sun region is explored by the upcoming Rubin Observatory's Legacy Survey of Space and Time (LSST), which has the potential to drastically increase the number of asteroid discoveries in the hottest part of the Solar System.
Another way that the gravitational influence of the planets over small bodies can dramatically modify asteroid orbits is by changing asteroid orbital inclinations (i.e., their angular tilt out of the plane of the Solar System) to the point that they orbit the Sun backwards, a process previously thought not to be dynamically possible. I will discuss what we know about how this dynamical phenomena works as well as how this population of asteroids can answer previously open questions about the origins of several rare, known Solar System small bodies. These small bodies include meteoroids, near-Earth objects, and asteroids that can get temporarily captured as Jupiter "Trojans". I will also discuss our efforts to identify more of these latter objects among the 300,000+ Jupiter Trojan discoveries anticipated from the LSST, which is expected to start its 10-year all-sky survey in late 2024.
Colloquium Speaker: Sarah Greenstreet
Sarah Greenstreet is a research scientist with the DiRAC Institute in the Astronomy Department at the University of Washington. She is the Lead for the Rubin Observatory Solar System Science Collaboration Near-Earth Objects and Interstellar Objects Working Group. Her research program primarily focuses on better understanding the origins, dynamical histories, future trajectories, and possible impact probabilities and crater formation rates of known small bodies and their larger populations across the Solar System. This includes near-Earth objects, main-belt asteroids, giant planet co-orbitals, and Kuiper Belt objects. During her time as a postdoc at Las Cumbres Observatory, she also used observations for near-Earth object follow-up and characterization as well as confirming that predicted asteroids undergo the Yarkovsky effect. She received her PhD in 2015 from the University of British Columbia.