I am keen to get the answer as to what is the Difference between gas composition of nebulae and gas planets like jupiter. Why doesn't jupiter explode or create stars like nebulae do. Do nebulae have something else going that gives birth to stars. 

4 hours ago, Layers said:

Why doesn't jupiter explode or create stars like nebulae do

Janus and others answered the same question in your other thread

3 hours ago, Janus said:

Hydrogen fusion, the process by which the Sun generates requires special conditions, as pointed out by chenbeier.( which is why we are having such a hard time developing fusion power plants.   Even our hydrogen bombs need a fission bomb as a trigger). It is estimated that you would need something between 70 and 80 times the mass of Jupiter to maintain fusion at the core. 

Comets hit the outer atmosphere of the planet where the gases are even more rarefied.  While these comets could provide the energy needed to ignite chemical combustion, Jupiter's atmosphere isn't combustible. For that you need something the burn (in this case the hydrogen), and something for it to chemically react with (like oxygen).   Jupiter's atmosphere has plenty of the first,  but is too deficient in the second to support such combustion.

 

How is the composition of nebulae different which gives birth to stars. How exactly does that happen and how's that different than jupiter. Thanks 

9 minutes ago, Layers said:

How is the composition of nebulae different which gives birth to stars. How exactly does that happen and how's that different than jupiter. Thanks 

https://en.m.wikipedia.org/wiki/Star_formation

 

Jupiter is short on the necessary hydrogen mass by about 100x. I would think the gas cloud supplying Jupiter depleted before it reached the required size.

Jupiter also from memory is thought to contain a planetary size rocky core bigger then Earth. This also from memory is why it has attracted such a dense atmosphere of the lighter gaseous elements. Pressures from the atmospheric gases is thought to be enough that hydrogen deep within its depths would be metalic.