History of the Universe

History of the Universe eBook. 398 pages, 300 illustrations only £5.99

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We have seen that a small red giant, up to 1.5 times the size of the Sun, turns into a white dwarf when it dies. Larger red giants, however, die in a more spectacular way.

Image of supernova remnant by NASA/ESA/JHU/R.Sankrit & W.Blair

Once the nuclear fuel is exhausted in a red giant, the core starts to cool and the internal pressure falls, leading to contraction. In large red giants this is a sudden and catastrophic event so that the star collapses. As the outer layers of the star fall they gain heat. This triggers nuclear fusion in these outer layers and they explode in a spectacular explosion called a supernova, becoming for a few days brighter than a whole galaxy.

With so much energy it is possible to fuse iron nuclei into even heavier ones such as uranium nuclei. As the star explodes it throws out the nuclei which it has made. On their way out they pick up electrons and become atoms.

The helium, oxygen, carbon, nitrogen, iron, uranium and other heavy atoms made by the star are scattered back to dust in the disc of the galaxy. In this way the atoms made in one generation of stars are passed on to be used by the next.

So all the atoms in your body (except hydrogen) were made in a supernova five billion years or more ago. In this story we will trace their history from the supernova to today. But first we will describe the fate of some different stars after their supernova stage.

What happens to them depends upon the size of the original star.

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History of the Universe eBook
History of the Universe eBook
Only £5.99

Written by Wyken Seagrave
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