Final answer:
The Sun's lifecycle includes the phases: protostar, main sequence, red giant, and white dwarf. Its lifespan largely depends on its initial mass, with larger stars having shorter lifespans. Throughout its life, the Sun's size, temperature, and luminosity will change, and its core will transition from fusing hydrogen to helium to eventually fusing helium to carbon.
Step-by-step explanation:
The Sun, like other stars, follows a life cycle that can be divided into several phases: the protostar stage, main sequence stage, red giant stage, and finally the white dwarf stage. Initially, the sun begins as a protostar, a large amount of gas that accumulates due to gravity until it begins nuclear fusion, where hydrogen combined to form helium. This is the main sequence stage and it's characterized by a balance between gravity pulling inward and pressure from fusion pushing outward.
The sun will stay in this stage for approximately 10 billion years. At this stage, its size, temperature, and luminosity are relatively stable. As the Sun's hydrogen supply starts to deplete, gravity will start to win over pressure and the core will begin to contract.
This will cause the rest of the Sun to expand and cool, becoming a red giant. At this stage, helium will start fusing into carbon and the Sun will grow much larger. After this phase, the Sun will eject its outer layer and leave behind a hot core, now a white dwarf. Eventually, this will cool and dim, becoming a black dwarf.
The life span of stars, including the Sun, depends primarily on their initial mass. Larger stars burn through their hydrogen supply more quickly and therefore have shorter lives. As for the sun, it's a medium-sized star with a predicted lifespan of around 10 billion years.
Learn more about Sun's life cycle