star birth

[claymore]

When a star first surges into life what prevents it from converting all of its mass into energy straight away, does the stars gravitational pressure prevent this from happening?

[jake-the-peg]

Gravity actually accelerates it.

The fusion reactions powering stars are dependant on the temperature and density

So the density is your damping factor. it's the fusion pressure working against the gravitational pressure that reduces the density and slows the reaction

[mibn2cweus]

. . . aka hydrostatic equilibrium

[Clanad]

Further to jake's helioseismologically correct answer, proto stars that don't quite make it to the size of our own sun ( 1 Msun ) in mass, become brown dwarfs Stars are classified in relation to their temperature and luminosity. Our own sun is a star classified as a spectral class G2 and its luminosity as class V .

By the way, some stars do (generally termed Massive Stars) (more than about 30 times the mass of our own sun) "burn up" quite quickly... some in less than a million years and when they "die" are now thought to be one of the two sources for the observed gamma ray bursts throughout the universe...

[Teddio]

There is no mechanism in a star for converting ALL of its mass into energy. During the nuclear fusion process heavier nuclei are formed which have a higher binding energy per nucleon and some mass is lost. This "lost" mass is converted to energy according to Einstein's well known equation.
The fusion process can be explained (along with most chemical reactions) by one of the simplest and most important equations in physics: Work = Force X Distance
Nuclei with weakly bonded nucleons form nuclei with strongly bonded nucleons: this applies to fusion and fission.

[beso]

The fusion only happens in the deepest parts of the star where the density and temperature is high enough to overcome the electrostatic repulsion of the positively charged nuclei.

The pressure of the radiation emerging from the reaction pushes against the gravity and prevents the rest of the hydrogen reaching the region where the fusion takes place.

When you consider the strength of gravity inside a star that is one hell of a bright radiation source.