12 October 2000 CfA Colloquium


Title: INTO THE DARK: The Long-term Fate and Evolution of Astrophysical Objects in a Dying Universe

Speaker: Fred C. Adams

Abstract: This talk outlines astrophysical issues related to the long term fate of the universe. We consider the evolution of planets, stars, stellar populations, galaxies, and the universe itself over time scales which greatly exceed the current age of the cosmos. This discussion starts with new stellar evolution calculations which follow the future development of low mass (M type) stars that dominate the stellar IMF. We then determine the final mass distribution of stellar remnants -- the neutron stars, white dwarfs, and brown dwarfs remaining at the end of stellar evolution. After 1-10 trillion years, the supply of interstellar gas becomes exhausted, yet star formation continues at a highly attenuated level through brown dwarf collisions. This process tails off as the galaxy gradually depletes its stars by ejecting the majority, and driving a minority toward accretion onto massive black holes. As the galaxy disperses, weakly interacting dark matter particles are accreted by white dwarfs, where they subsequently annihilate with each other and thereby keep the old stellar remnants relatively warm. After accounting for the destruction of the galaxy, we consider the fate of the expelled degenerate objects (planets, white dwarfs, and neutron stars) within the assumption that proton decay is a viable process. The evolution and eventual sublimation of these objects is dictated by the decay of their constituent nucleons, and this evolutionary scenario is developed in some detail. After white dwarfs and neutron stars have disappeared, galactic black holes slowly lose their mass as they emit Hawking radiation. After the largest black holes have evaporated, the universe slowly slides into darkness.

Reference for students: TBA

Lunch with the students will be on Thursday, October 12 at 12:30 in A-101.