This week, Hubble Postdoctoral Fellow Andreas Kupper described the dynamics of multiple massive objects in the same system. When two massive objects are near each other, they exert gravitational forces on each other and their motions can be described analytically - that is, the motions at all times can be calculated by hand from basic theories. When three or more massive objects interact gravitationally, the interactions become complicated and can only be modeled using computer simulations. Andreas showed the results of a few of his simulations - after the objects orbit chaotically around each other for a while, one object (usually the one with the lowest mass) is thrown out of the system with a very high velocity. The remaining objects end up closer together, and this process, called scattering, is thought to be responsible for bringing massive objects like black holes and neutron stars close enough together that they can merge into an even more massive object.
After the lecture, audiences were treated to a showing of LIGO: A Passion for Understanding, a 20 minute film about a project to detect gravitational waves coming from closely interacting massive objects. After the film, graduate student Aleksey Generozov and I answered questions about gravitational waves and LIGO. Graduate student Yong Zheng was the roof captain, sharing glimpses of the Moon, Albireo and the Ring Nebula while undergraduate Pratishta Yerakala took attendees on a 3D tour of the Universe with the 3D wall.
-- Steph Douglas (graduate student)