Fuel, stars

Releasing fusion energy on a human scale requires fusion fuels that react vith each other more rapidly than the slow-burning basic fuels of stars. 

The sun and all other stars produce energy at a huge rate from sustained nuclear fusion. Over time, stars evolve through several stages, including stellar explosions. The products of a stellar explosion can form stars of more complex composition. Three distinct generations of stars have been identified, each fueled by a different set of fusion reactions. 

About 10 years after fusion of helium begins, a star mns out of He fuel. When this happens, the star enters a... 

The overall abundance of helium and heavy elements in the Universe today. This reflects the total effect of fuel consumption and nucleosynthesis by all the stars that ever existed. Roughly speaking, one may consider this in two... 

It has been claimed that the second law means that the universe as a whole must tend inexorably towards a state of maximum entropy. By an analogy with a closed system, the entire universe must eventually end up in a state of equilibrium, with the same temperature everywhere. The stars will run out of fuel. All life will cease. The universe will slowly peter out in a featureless expanse of nothingness. It will suffer a heat death . 

The emission of a helium nucleus in the final stage regenerates the initial carbon-12. The latter thus plays the role of a catalyst. The overall result is the fusion of four protons into a helium nucleus. At high temperatures, this cycle dominates over the proton-proton chain. Indeed thermal agitation facilitates penetration of the relatively high electrical barrier between proton and carbon nucleus. Whatever hydrogen fusion mechanism is prevalent, the star s mass determines the rate at which it consumes its nuclear fuel, and hence also its lifetime. The higher its mass, the more quickly it bums. 

Conseqnently, well before the Snn rnns ont of hydrogen fuel, life will take its final bow, at least, if we are to believe these nnmerical simnlations. What will happen to the planet which life leaves behind it Until very recently, astronomers believed that the Snn wonld lose enongh mass through its red giant winds to ensnre that the Earth s distended orbit wonld not be absorbed by the swelling star. The fate of the Earth thns hangs npon the dying breath of its star. In fact,... 

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