At the core of the sun is a controlled nuclear explosion, producing a temperature of 15 to 20 million degrees or so. This great temperature and outward radiative pressure, in balance with the intense gravity at the core, maintains the nuclear fusion of hydrogen that causes our sun to shine. However, the physics at the surface of the sun are quite different. All the intense heat stays in the core. That which makes it to the surface only does so by convection, the same process that occurs as tomato sauce simmers on a hot stove.
Astronomers can watch the same phenomena on the sun.
Also they can see the dark spots that Galileo discovered so long ago. That is why they appear dark. If they were isolated from the surface of the sun, they would appear as bright as the surface themselves. An intense magnetic field in the sunspot area prevents hot material from flowing into it, thereby allowing it to cool somewhat. You could consider the sunspot is the shade of a tree on a sunny day here on earth.