• Question: why do stars die?

    Asked by pollystyrene to Nazim, Adam, Catherine, Karen, Leila on 15 Mar 2012. This question was also asked by isobel2302.
    • Photo: Adam Stevens

      Adam Stevens answered on 14 Mar 2012:

      Stars start off burning hydrogen for their fuel. Eventually this runs out so they have to burn heavier elements. Eventually all the fuel in the star gets turned into heavier and heavier elements, that are not as good a fuel as the hydrogen they started off with.

      At some point the star will either totally run out of fuel, or have turned all its fuel into Iron, which it can’t use to burn anymore. That’s when it dies.

    • Photo: Leila Battison

      Leila Battison answered on 15 Mar 2012:

      I don’t like to think of stars dying, but *evolving*!

      New stars are burning lots of hydrogen and creating more elements inside them, like carbon and iron. Then when there is more of these elements than hydrogen, they get burnt up, until, like Adam says, only iron is left. I guess that means that that star has dies, but its been replaced with another awesome Iron planet! Ok, maybe not as exciting, but still not completely disappeared.

      If the star is big enough, it will get hotter and hotter and explode into a superenova before it runs out of fuel. Then it is definitely not dying, but giving birth, because it scatters all its elements into space where new stars can start forming, and everything begins again!

    • Photo: Karen Masters

      Karen Masters answered on 15 Mar 2012:

      Bascially they run out of fuel. A normal star fuses hyrogen into helium in its core to generate energy. Once all the hydrogen has gone the star will collapse a bit more until it can start burning helium, and will keep doing this until it either is not massive enough to generate the temperature needed to fuse the next element, or until it hits iron (which does not generate energy if it fuses). If the former the star will gently puff out into a gas cloud an leave a white dwarf behind. If the latter there will be a dramatic collapse and a rebound (which we call a supernova) and either a neutron star or a black hole is left behind.

    • Photo: Nazim Bharmal

      Nazim Bharmal answered on 15 Mar 2012:

      Stars die when they run out of fuel in their interior. Basically, without fuel, they can’t keep their nuclear reaction going which usually keeps gravity from collapsing the star.

      (Imagine a balloon that has a tiny hole in it; you have to keep blowing to stop the air pressure from the outside deflating it, and when you stop it will shrivel up.)

      So when the reactions stop you can get; a slow cooling down if the star is small; the type of nuclear reaction can change, the star gets huge and red (this is what will happen to our Sun), and then shrinks to a small star that slowly cools; an explosion (supernovae) that produces a new, smaller star that slowly cools; or the most dramatic option is a bigger supernovae that leaves a neutron star or a black hole.

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