stars

[Boogeyman]

Stars eventually die because they use up their fuel right? If all of this fuel was to be used up, would there be no suns?

[mgb_phys]

Stars eventually die because they use up their fuel right?
They convert elements into other elements extracting some energy.
Different size suns (and the same sun at different times during it's life) use different elements, so larger red suns can burn the 'waste' of smaller hotter suns.

If all of this fuel was to be used up, would there be no suns?
Ultimately all the elements could be burned to the point where there is no more energy to be extracted by burning them further - there would only be iron and heavier elements left.

- that's going to take a while though :-)

[Boogeyman]

Yeah I know but if it happens that would mean death of life, and a cold universe?

[russ_watters]

Yes. Consider the ironically termed "heat death" scenario for the universe: http://en.wikipedia.org/wiki/Heat_death_of_the_universe

[qraal]

Yeah I know but if it happens that would mean death of life, and a cold universe?

Yes it does, as the Universe keeps expanding it cools, thus when the stars finally go out it will be very cold... but not everywhere. Every hundred billion years or so brown dwarfs will collide with each other or with a white dwarf and produce a new star that will last ~0.1-10 trillion years. Roughly a hundred such dim stars will burn in our Galaxy at a time, for about 10,000 quadrillion years until the Galaxy falls apart. After that happens the hottest things will be neutron stars "glowing" at 3 K from proton-decay... very, very cold.

But we don't yet know if the Universe will last that long - it might recollapse due to some cosmic change.