What are the differences between the sun and a red giant?

The sun is approximately 4.6 billion years old. After another 5 billion years, all of the hydrogen in the sun will burn and the helium will begin to burn. At that point, the sun will transform into a red giant star. Mass will decrease, the gas will expand, and the star will become a red giant. It will first reach the orbits of Mercury and Venus. Consequently, the red giant stage will be the end stage of the main sequence.

The main differences between the sun and a red giant lie in their size, temperature, and stage of life. Red giants are much larger and cooler than the sun, with diameters tens to hundreds of times greater. They are in a later stage of their life cycle, characterized by the depletion of hydrogen fuel in their cores and the expansion of their outer layers. As a result, red giants have lower surface temperatures than the sun.