Does the sun grow every year?

Answer

Indeed, the sun has increased in radius since its formation 4.5 billion years ago. The radius has since increased by about 13%, which amounts to about 90 thousand kilometers. On average, that corresponds to about 2 centimeters per year. In the beginning it was a little slower, and now a little faster, but that 2 centimeters per year is a good approximation.

In about 6 billion years, the sun’s radius will increase more rapidly: in a few hundred thousand years it will become five times as large as it is today. The sun then becomes a so-called ‘red giant’. During that period, it will therefore increase by an average of more than one kilometer per year.