Why doesn’t the Sun explode?

Some basic facts about Sun

In the universe, the most massive star is about 100 solar masses and the least massive star we know about
is about 0.1 solar masses. Sun rotates about once every 27 days on average. The poles rotate every 24 days The equator rotates every 30 days. The surface temperature of the Sun is ~5500 K and the Central temperature is about 15 million Kelvin. Sunspots are slightly cooler, So they appear dark.

This image was captured by NASA’s Solar Dynamics Observatory. Image Credit: NASA/SDO

Why Sun is in equilibrium?

The sun is in “Hydrostatic equilibrium” because Upward pressure(Nuclear Energy) balances downward pressure(Gravitational energy). The sun is a perfect gas which means that there is a lot of space between individual particles. The pressure of perfect gas can be defined by the Perfect Gas Law P=nkT, where n is the number of molecules or the number of atoms per unit volume and K is Boltzmann’s Constant. Inward Pressure is Gravity( g=GM/r²).

The present radius of the sun has just the right value to maintain a central temperature that provides a nuclear energy generation rate that exactly balances the loss of photons traveling from the center to the surface.