heat transfer in stars

[Lizzzza]

I can't understand why heat is transfered differently in low and high mass stars. I read that radiation is more efficient when the gaz is already ionized, meaning it's really hot, then I understand why the core of the Sun is a radiative zone. But I don't see why it wouldn't apply to high mass star? why in this case is the core convective??

Thank you for your help!!

Edited July 14, 2019 by Lizzzza
mistake