Question

. How much of its fuel has the Sun used up?

Answer 1

The Sun has used up about half of its Hydrogen fuel.

Explanation:

The Sun started out being about 73% Hydrogen and the rest Helium. It is a main sequence star which means it is fusing Hydrogen into Helium in its core.

Most of the Sun is 70% Hydrogen. Its core which is 25% of the Sun's radius is down to about 33% Hydrogen at its centre. It is only in the core and the regions around it where fusion reactions can take place.

The Sun is currently about 4.6 billion years old. It will run out of Hydrogen in its core in 5 to 6 billion years and become a red giant.

So, the Sun has used up almost half of the Hydrogen fuel required for fusion reactions to take place in its core.