A radiative zone where photons carry energy upwards. A convective zone in the outer third of the Sun, where columns of warm gas rise and hot gas sinks. Graphic: Derek Homeier, Univ. Of the questions we set for ourselves was: how long will the Sun last? If the Sun was able to convert all its hydrogen completely to helium, it would take about 100 billion years to burn out. The Sun is about 5 billion years old, so it has 95 billion years left… Right? Wrong! As the Sun fuses more and more hydrogen, its internal structure changes; it becomes hotter and hotter, eventually swelling up into a red giant star which will envelop the inner solar system. This is predicted to happen in about 5 billion years from now. Helium burning in the Sun?