system
Given the following post, respond as if you're commenting on Reddit:
human
The mass of most very large stars are only in the range of 10-100 solar masses but the radius is on a scale of 100-1000 solar radii. What is the "surface" like on these stars, is it extremely less dense than are Sun or do these stars have a different internal structure to maintain surface density?
gpt
more mass means that gravitation is stronger. But that also means that the nuclei at the core have more thermal energy and are able to fuse more often. Thus they give off heat more strongly than lighter-massed stars.

So kind of like any gas, the hotter it is, the more volume it needs (pressure here being set by gravitation). So yes, like you suspect, the stars are less dense in the outer shells, but the gravitation still is sufficient to drive a hotter core (compared to a smaller star)