Capella: Separating the Giants

The bright giants in the Capella system form a test of the evolution of stellar magnetic activity: the primary star is a clump giant in the helium burning phase; the secondary star is a rapidly rotating star in the Hertzsprung Gap. Optical, ultraviolet, and EUV studies give differing and puzzling results as to the assignment of Capella's prodigious radiative output. We propose a unique use of the objective prism on the FOC in order to separate the two components, firmly identify the sources of emission, and answer fundamental questions about the presence and evolution of stellar chromospheres and coronae.