Black holes and neutron stars: Probing the laws of physics with extremely compact objects

Black holes and neutron stars are among the most extreme objects that we can observe today. Neutron stars are more massive than the sun, and yet smaller than many cities. Observing them allows us to study the laws of physics in conditions currently unattainable in laboratories on earth. Their huge density, in particular, offers the opportunity to test our understanding of gravitational interactions in Einstein's theory of general relativity, and of nuclear physics. Black holes are even more compact - so much so that even light cannot escape their gravitational attraction, and that they can only be observed through their effects on nearby gas, stars, and other black holes. Like neutron stars, black holes can be great laboratories to study gravity. Some are only a few times more massive than the sun, but the centers of many galaxies are occupied by extremely massive black holes, of millions to billions of times the mass of the sun, which have a profound but still poorly understood effect on the evolution of galaxies and the formation of stars.

In this talk, I will review the formation of black holes and neutron stars, how we observe these objects, and the impact of these observations on our understanding of gravity, nuclear physics, and astrophysics. I will also discuss what happens when two of these objects collide in extremely energetic events, which can produce bright but short-lived emission of light, as well as "gravitational waves" - ripples of spacetime produced by the interaction of massive objects, which have been predicted by Einstein's theory of general relativity and are expected to be detected for the first time in the next 5 years.

Speaker: Francois Foucart, UC Berkeley