system
Given the following post, respond as if you're commenting on Reddit:
human
Are the blackholes in center of galaxies formed by super gigantic stars?

I understand that if a star is huge in mass it can form a blackhole and that at the center of the galaxy there is a blackhole. Does that mean that, for example at the center of the Milky Way, there was once a gigantic star that has collapsed? Or is it more likely that it was a blackhole that has simply gotten bigger over time.

Wouldn't there be a threshold as well to as of how big a star can be before it becomes a black hole or is it simply just how much fuel it has?
gpt
The black hole in the galactic centre (Sg A*) is far too massive to have formed from a single star (it is of the order of a few million solar masses, stars are rarely found above a hundred solar masses due to stability). Thus, it must have grown over time from coalescing black holes plus accreted matter.

This is actually a major area of research, because there is a 'missing link' stage in black hole growth between stellar mass black holes and supermassive black holes, which to date nobody has been able to find evidence for.