system
Given the following post, respond as if you're commenting on Reddit:
human
If we shot Jupiter and Saturn into the sun, roughly how much longer would the sun undergo fusion before turning into a red giant?

Both Saturn and Jupiter are composed primarily of hydrogen and hydrogen is the main element 'used' by the sun to sustain fusion. If both Saturn and Jupiter were shot into the sun and they were 'absorbed' cleanly by the star, how much longer than normal would the sun undergo fusion before it turns into a red giant?

I'm asking because I need a contingency plan just in case I happen to survive the next 5.7 billion years.
gpt
You've got it backwards. You want to take mass *away* from the sun to make it live longer. The more massive a star is, the shorter its lifetime. This happens because the extra gravitational pressure from added mass increases the rate of fusion in the core a lot, so even though there's more hydrogen/helium, you burn through it way faster.

The lowest mass stars have predicted lifetimes of well over a trillion years. The highest mass stars have lifetimes less than a million years.

Changing the mass of the sun by +/- the mass of Jupiter+Saturn (about 0.1% of a solar mass) probably won't change the lifetime by more than a few million years though.