Grant: Discovery Grants Program - Individual

Our knowledge of the structure and evolution of stars has increased greatly with the advent of high powered digital computers. We have understood the basic life cycle for stars for about four decades now, but our failure to match increasingly refined observations demonstrates that we do not understand everything. For example, the traditional models predict neither the enhancement of the surface abundances of some elements which must be created deep inside the star and transported to the surface nor the correct values for all the observed oscillation periods of stars appreciably more massive than the sun.Rotation, not included in the traditional models,  has been identified as the possible reason for these discrepancies. This may come not only through the alteration of the stellar structure produced by the rotational force, but also through short and intermediate time scale motion produced by instabilities that rotation can cause. The motion produced by these instabilities transports material and angular momentum throughout the star.  The multi-dimensional calculations proposed in this research can be expected to reproduce the stellar structure adequately for a given angular momentum distribution. With some further development, it is expected that the evolution of the composition and angular momentum distributions produced through these rotational instabilities can be followed as well. This should allow us to narrow the possible angular momentum distribution possibilities that stars have. This redistribution of material and angular momentum begins early in the star's life. Later stages of stellar evolution will be affected by this and this may be the key to understanding some discrepancies between observation and models in these later phases as well.The computational methods utilized have application in many other areas of research: climate studies, turbulence research, and defense related work.