Colloquium: Dr. Tim LawlorDr. Tim Lawlor Department of Physics Penn State Brandywine Media, PA 19063
Early Universe Stars
Population III (Pop III) stars were the first stars to form in the universe and were presumably made from primarily hydrogen, and some helium. It is generally believed that the first stars were very massive, in the range of 100 - 1000 solar masses. While there is consensus that the "first" stars were very massive, radiation feedback from these may have induced the production of lower mass population III stars. There has so far been no direct observation of any metal free star. They are expected to be very far away and for lower masses, were probably quickly contaminated with metals expelled by other exploding stars. A growing body of work exists on the numeric modeling of the first massive stars, but less has been done for mid-mass Pop III stars (in the range of 10 – 60 solar masses). We present a review of early universe stars and our numerical evolution results for mid-mass Pop III stars. Our evolution models are evolved from pre-main sequence to main sequence (hydrogen fusion in the core) through the end of the red giant phase (silicon fusion in the core). We further use the final stellar structure from our evolution models for numerical simulations of their resulting supernovae light curves. We plan to compile a large grid of models along with their resulting supernova light curves in expectation for the eventual discovery of a first star (or a first star's explosion). Observing campaigns such as the 2018 launch of the James Web Telescope should push observations ever closer to direct observation of the early universe stars.