The Future of the Universe and its Present-Day Implications
This talk describes our current picture for the long term fate of the cosmos. This discussion includes the evolution of planets, stars, galaxies, and the universe itself over time scales that greatly exceed the current age of the universe. We find that studying the physics relevant to the future provides a richer understanding of present day astrophysics. The story begins with the effects of accelerated cosmic expansion, which causes every galaxy cluster to
become its own island universe in the ``near'' future. This work leads to several insights regarding the structure of dark matter halos, including the orbits of their constituent particles. Next we discuss long term stellar evolution with a focus on stars with the lowest mass. Since these stars do not become red giants, the study of their future evolution leads to greater understanding of the processes that cause solar type stars to become giants. After star
formation ends, we find the mass distribution of the neutron stars, white dwarfs, and brown dwarfs remaining after stellar evolution has run its course.
However, new stars can be produced at an attenuated rate through brown dwarf collisions. This process tapers off as the galaxy loses its stars, primarily by ejection through scattering encounters. During this epoch, dark matter particles are accreted by white dwarfs, where they annihilate and keep the old stellar remnants ``warm''. After the demise of the galaxy, the expelled degenerate objects evaporate via proton decay. When these stellar remnants are gone, black holes are the brightest astrophysical objects, slowly losing mass as they emit Hawking radiation. After the largest black holes have evaporated, the universe slowly slides into darkness.
