Question: how many years will it be until the sun changes state?

Christie Waddington answered on 17 Jun 2016:

It is thought that the Sun will become a Red Giant in about 7.6 billions years, so loads of time yet! In this state, the sun will stop burning the hydrogen into helium in its core and instead start burning the hydrogen that surrounds it. The helium begins to burn into carbon, which causes the sun to increase in size (puff out I guess) which lowers its temperature and it appears red. It may engulf Mercury and Venus at this point!