Star loses its energy constantly due to continuous emission of light and energy. This means that the temperature of a star decreases continuously and hence its gas pressure which thereby decreases its stability. … This burning and therefore the decrease in the amount of fuel is the reason for the evolution in the stars.

Why do stars eventually change?

The fusion of hydrogen to form helium changes the interior composition of a star, which in turn results in changes in its temperature, luminosity, and radius. Eventually, as stars age, they evolve away from the main sequence to become red giants or supergiants.

Why stars evolve and the reasons for this evolution in their lifetime?

Exactly how a star evolves depends strongly on its mass. Stars more massive than the Sun are like rock stars — they burn brightly and die young. … If gravity wins, the star collapses, if pressure wins, the star expands. Stars spend most of their lifetimes in a steady state when these two force balance each other.