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Special Guest Seminar - spring-2024

Orbital Architecture of Planetary Systems Formed by Gravitational Scattering and Collisions

May 14, 2024
2 p.m. - 3 p.m.
3814 Geology

Presented By:

  • Eiichiro Kokubo - NAOJ
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In the standard formation models of terrestrial planets in the solar system and close-in super-Earths recently discovered by exoplanet observations, planets are formed by giant impacts of protoplanets or planetary embryos after the dispersal of protoplanetary disk gas in the final stage. This study aims to theoretically clarify a fundamental scaling law for the orbital architecture of planetary systems formed by giant impacts. In the giant impact stage, protoplanets gravitationally scatter and collide with each other to form planets. We investigate the orbital architecture of planetary systems formed from protoplanet systems by giant impacts using N-body simulations. As the orbital architecture parameters we focus on the mean orbital separation between two adjacent planets and the mean orbital eccentricity of planets in a planetary system. We find that the orbital architecture is scaled by the epicycle amplitude for the eccentricity given by the ratio of the two-body surface escape velocity of planets to the Kepler velocity. With this scaling the orbital architecture parameters are independent of the total mass and semimajor axis of planetary systems.

Fostering Science Innovation and Inclusion in the Geosciences

May 23, 2024
2 p.m. - 3 p.m.
3853 Slichter Hall

Presented By:

  • Aaron Velasco - University of Texas
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This talk explores the use of collective impact, a model for community engagement, to advance science and to make science responsive to community needs, especially communities that have traditionally been underserved. The status of geosciences in terms of diversity will be presented, highlighting where progress has been made, and the current climate for minority geoscientists. I will introduce collective impact as a means of advancing science, and creating a culture of inclusion that, we hope, will transcends deficiencies in the culture of modern science. The collective impact approach develops a network of community members, organizations, and institutions through the framework of a common agenda, centralized support, continuous communication, mutually reinforcing activities, and shared measurement. I will introduce the Center for Collective Impact in Earthquake Science (C-CIES), a National Science Foundation funded Centers of Innovation and Community Engagement planning grant, which has the vision to become a leading-edge earthquake research center dedicated to improving resiliency from seismic hazards in an equitable, accessible, and sustainable manner. The mission will be to advance earthquake science with the aim of meeting the natural hazard mitigation needs of all communities in regions high consequence, low frequency of incidence (Hi-C-LoFi) earthquake risk. I will explore a specific project in El Paso, TX on the East Franklin Mountains fault, which has a potential for a M6.5-7.0 earthquake, and the science and community input that drives the project.