Question

when and why do a star becomes redgiant?

Answer 1

Red giant stars. Our sun is a type of star called a yellow dwarf. It has been shining for nearly five billion years, and has enough hydrogen fuel to last another five billion years. The sun and other stars eventually begin to run out of hydrogen.A red giant star is a dying star in the last stages of stellar evolution. In only a few billion years, our own sun will turn into a red giant star, expand and engulf the inner planets, possibly even Earth.