I understand the Sun consumes 600,000,000 tons of Hydrogen each second. Where is this Hydrogen? Is all the Hydrogen the Sun will ever consume inside it or are there vast amounts of Hydrogen in space that the Sun is somehow sucking up and consuming?


By "consume" we mean "convert into helium." That $6\times10^{11}\ \mathrm{kg}$ of hydrogen is part of the Sun (specifically it is found in the core of the Sun), and it is converted into $6\times10^{11}\ \mathrm{kg}$ of helium. The Sun doesn't need to suck up material from space.

Note that this amount of material is miniscule compared to the $2\times10^{30}\ \mathrm{kg}$ mass of the Sun. That is, the Sun converts its mass to another element at a rate of only one part in $10^{18}$ each second, or one part in $10^{11}$ each year, or about 1% per billion years.

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    $\begingroup$ Right. And the Sun not only "doesn't need" to suck material from space. It would have no effective way to do so, either. The Sun holds 99.8% of the mass of the Solar System - outside the Sun, this large volume of the Universe is really really empty. $\endgroup$ Aug 17 '15 at 5:16
  • $\begingroup$ Now I'm confused as I don't really know the elemental composition of the sun. What is the percentage breakdown? Is it all just the Helium and Hydrogen? $\endgroup$ Aug 17 '15 at 5:21
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    $\begingroup$ @Steve 74.9% hydrogen and 23.8% helium, by mass. This is about what you find for everything in the universe except rocky planets like Earth. $\endgroup$
    – user10851
    Aug 17 '15 at 5:31

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