Stellar evolution is the process by which a star changes over time, extending from its formation to its death. It consists of several distinct stages, depending on the initial mass of the star.
For low- to intermediate-mass stars, like our Sun, the evolutionary pathway includes:
- The Main Sequence Phase, where hydrogen fusion occurs in the core, providing energy and radiation pressure to combat gravity.
- Red Giant Phase, when the core runs out of hydrogen, causing the outer layers to expand and cool.
- The AGB Phase, which we covered earlier, characterized by pulsations and mass loss.
After the AGB phase, the star sheds its outer layers, forming a planetary nebula, and leaves behind a hot core.
Understanding stellar evolution helps us to comprehend the lifecycle of stars and the recycling of material within galaxies. It also provides insight into the formation of different celestial phenomena, such as nebulae and white dwarf stars.