MPS Seminar: Stellar Evidence of a Transitional Sun (T. Metcalfe)

Precise photometry from the Kepler space telescope allows not only the measurement of rotation in solar-type field stars, but also the determination of reliable masses and ages from asteroseismology. These critical data have recently provided the first opportunity to calibrate rotation-age relations for stars older than the Sun. The evolutionary picture that emerges is surprising: beyond middle-age the efficiency of magnetic braking is dramatically reduced, implying a fundamental change in angular momentum loss beyond a Rossby number Ro~2. I will review detailed evolutionary modeling of the Kepler observations and discuss recent attempts to expand the sample and minimize systematic uncertainties. This will provide the context for a broader discussion of the multiple lines of evidence that the Sun is in a transitional evolutionary state, and that its magnetic cycle must represent a special case of stellar dynamo theory.