Final answer:
Astronomers study stellar evolution indirectly by observing star clusters, where stars of different masses and evolutionary stages coexist. They use computer models to simulate star evolution, and they examine the remains of dead stars to validate their models. This multifaceted approach enables a complete understanding of stellar life cycles.
Step-by-step explanation:
Astronomers overcome the limitation of not being able to follow the life-cycle of an individual star due to its long timescales by employing a combination of methods. Star clusters play a crucial role in this process. When astronomers observe a cluster, they are essentially looking at a snapshot of stars that formed around the same time from the same cloud and with the same composition, but of different masses. These different masses result in stars that evolve at different rates, allowing astronomers to see various stages of stellar evolution within the same cluster. By analyzing these stages, astronomers can create a more complete picture of a star's life cycle.
In addition to real-time observation, astronomers use computer models to simulate the processes involved in stellar evolution. These models are tested against observations of star clusters and the remains of dead stars, such as white dwarfs, neutron stars, and black holes, to ensure they accurately reflect the physical processes happening in stars. Together, these approaches provide a comprehensive understanding of the stellar evolutionary process despite the prohibitive timescales of direct observation.