Rationalised 2023-24
317
Nuclei
The age of the sun is about 5×109 y and it is estimated that there is
enough hydrogen in the sun to keep it going for another 5 billion years After that, the hydrogen burning will stop and the sun will begin to cool
and will start to collapse under gravity, which will raise the core
temperature The outer envelope of the sun will expand, turning it into
the so called red giant 13