 Part of the SIM's mission is to provide pinpoint measurements for the two extremes in stellar mass and evolution. The telescope will not be able to measure the mass of every star in the Galaxy, since there are over 200 billion, but instead, it will take a "population census." Through this technique, SIM will be able to output accurate masses for representative examples for nearly every star type, including brown dwarfs, hot white dwarfs, red giant stars, and elusive black holes. Current space telescopes, including NASA's Hubble Space Telescope, can accurately measure mass for some types of stars, but not all. Estimates put the range for stellar mass somewhere between 8 % the mass of the Sun and in excess of 60 times the mass of the Sun. The entire study will be focused on binary star systems, stars coupled through a mutual gravitational attraction.
