Final answer:
The aging process of a star is known as its evolution, which for a star like the Sun includes phases such as the main-sequence, red giant, and finally the white dwarf stage, where nuclear fusion ceases and the star cools over time.
Step-by-step explanation:
The aging process of a star is referred to as its evolution. The evolution of a star with a mass similar to that of the Sun involves several stages. While in the main-sequence phase, the star generates energy through the conversion of hydrogen into helium in its core. As the star exhausts its hydrogen, it leaves the main sequence to become a red giant, where its surface temperature decreases but its luminosity increases due to the expansion of its outer layers.
Following the red giant phase, the star undergoes a helium flash, after which it experiences a period of stability as helium is fused into carbon and oxygen. During this stage, the star becomes hotter and less luminous than it was as a red giant. When the helium is depleted, the star becomes a red giant again, signaling the approach of its end as it becomes brighter and cooler.
Ultimately, when a star like the Sun has exhausted its nuclear fuel, it sheds its outer layers and the core collapses under gravity, becoming a white dwarf. This final stage is marked by the cessation of nuclear fusion; the white dwarf cools and dims over billions of years, slowly fading away.