The Death of a Large Star
You may want to have a look at the first part]
| Very big stars (more than 5 times bigger than the Sun) can become a Red Giant several times. This is because when one type of nuclear fuel runs out (for example Helium), the centre of the star shrinks a bit more, becomes even hotter and a new fuel can be "burnt" (eg Carbon, Neon, Oxygen and so on). |
| Eventually, though, there will be nothing left that can be burnt. Then, gravity takes over and the very centre of the star collpases very fast. In fact, it collapses so fast that all the atoms in the centre are crushed together and destroyed and there is a massive explosion. |
| This explosion is called a Supernova. It is probably the most dramatic event in the universe - in a small fraction of a second the star will produce almost as much light and energy as it had done in its entire life up to then! One supernova can be as bright as an entire galaxy of 100,000,000,000 stars! |
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The Supernova explosion blows away the outer parts of the star leaving the
crushed core. This core is now one of the strangest objects in the known
universe.
If the star was about 5 to 20 times the mass of the Sun before it exploded, the core is crushed down so much that it is no longer made of atoms and becomes a neutron star. However, if the star was more than about 20 times the mass of the Sun, it will not stop collapsing even as a neutron star, and it will all crush down into one place and become a Black Hole! |
| If we now move very far away from the site of the explosion we can see what has happened to the bits of the star that were blown off. They are still moving away from the explosion and are glowing as they collide with the gas between the stars to produce beautiful Supernova Remnants (SNRs) like the Vela SNR shown here (Picture © Royal Observatory Edinburgh and the Anglo-Australian Observatory). |
