Why are HR diagrams of star clusters (like those in Diagram # 1) useful for studying stellar evolution?
• stars in clusters are approximately the same age. • stars in clusters have approximately the same composition. • stars in clusters have different masses. • all of the above are true. • Why do nova only occur in binary star systems? • Nova explosions require mass transfer to trigger the explosion. • Nova explosions require additional angular momentum from the companion star to occur. • Nova explosions do NOT occur only in binary star systems. • Only type-I nova explosions occur in binary star systems. • What happens to a very massive star (ten solar masses) when it runs out of Hydrogen in its core? • The core expands and heats up. • The core contracts and heats up. • The core expands and cools. • The core contracts and cools. • What causes a type-II supernova? • The explosion of Hydrogen rich material on the surface of a white dwarf. • We don’t know. Type-II supernova are a complete mystery. • The collapse of the iron core in a single, massive star. • The carbon detonation of a white
