All stars are big balls of glowing gas, powered by nuclear fusion. But stars come in many different sizes, masses, and colors. And they’re put together in different ways.
The Sun is in the middle range. It consists of three main layers — the core, the radiation zone, and the convection zone.
The core is where a star generates energy. Stars in the prime phase of life “fuse” hydrogen atoms to make helium, releasing energy in the process.
In the Sun, the core is surrounded by the radiation zone, where energy from the core travels outward. It can take hundreds of thousands of years for that energy to pass through the zone.
Finally, there’s the convection zone, which is like a pot of boiling water. Huge bubbles of hot gas rise from the bottom of the zone to the top, releasing energy into space.
Stars that are much less massive than the Sun have only the core and the convection zone. Such stars generate powerful magnetic fields, which produce dark “starspots” and enormous explosions of particles and energy. That can be bad for any planets that orbit the stars.
On the other hand, stars that are a few times more massive than the Sun are just the opposite. They have a deep radiation zone, but no convection zone. Those stars generate only a weak magnetic field, if any. So there are no big storms to pelt any orbiting planets.
When a star moves out of the main phase of life, its structure changes dramatically. But that’s a tale for another day.