# How do stars survive their own gravitational pull?

I read that stars burn hydrogen and helium to fight against gravity. How does burning something help against gravity?

• In the centre of the star is a nuclear fusion reactor, which emits radiation especially heat, which pushes the gas outwards against gravity. Also compressing the gas causes outward pressure. Nothing burns like a fire, burning means nuclear fusion in the case of the sun. If you read this link it might help. astronomynotes.com/starsun/s7.htm – user108787 Sep 9 '16 at 19:20

The (spherically symmetric) hydrostatic mechanical equilibrium condition is that $$\frac{dP}{dr} = -\rho g,$$ where $P$ is the pressure, $\rho$ the density and $g$ the inward gravitational acceleration, at a point that is a distance $r$ from the centre of the star.