Q Black holes emit no light, thus we cannot observe them directly with telescope observations. Despite this limitation, name & explain the three methods that allow astronomers to indirectly detect the existence of black holes using telescopes. 90% of all stars are part of a specific group in the H-R Diagram that all have a density similar to water. 1. Name this group 2. List all spectral classes (from coolest to hottest) within the group 3. Describe which spectral class, within this group, is smallest in size