Question

How can you determine that a star is about to turn into a red giant?

Answer 1

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

Answer 2

it lacks fuel (hydrogen) it burns helium

Step-by-step explanation:

Stars that are in a late cycle, will enter another stage known as Red Giants. The red giant will be tremendously brighter.

This happens since, helium sustitues the hydrogen that before was burning for millions of years. The red giant will grow bigger and bigger to enter the next stage shown in the image. See below :)