system
Given the following post, respond as if you're commenting on Reddit:
human
Would it be possible for a 'dead' star to gather enough mass from it's surrounding to restart the fusion cycle and effectively 'seed' a new star?

...and if not, why not?
gpt
Sort of, but not really.

Take the case of a white dwarf star which gathers mass from a close main sequence neighbor. The mass will pile up, sometimes you'll get a nova as the piled up mass undergoes a flash fusion reaction rather rapidly. However, if you keep on piling on mass eventually you'll start to raise the temperature of the core, and you'll get a period of convection. And then you'll start to get Carbon fusion in the core. Hey, the star is coming back to life! Right? Not exactly. In a white dwarf star the matter is under electron degeneracy conditions, which means that it's already at the maximum possible pressure, so the normal method of increasing temperature causing an increase in pressure causing expansion causing cooling which would serve as an escape/regulation valve for the energy of fusion simply doesn't work.

Instead what happens is the pressure remains constant and the energy released from the fusion reactions increases temperature, which increases the rate and extent of fusion reaction. This is a positive feedback loop which rapidly ticks over from fusing Carbon to fusing Oxygen and in fact a significant fraction of the total amount of Carbon and Oxygen in the star is burned up in fusion reactions in a matter of seconds. This releases more energy than the gravitational binding energy of the star, consequently the star blows itself apart in a Type Ia supernova.