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Asked by coolthew to Nick, Alan, Deepak, Francesca, Lilly on 18 Mar 2014. This question was also asked by simone2001, lillypop18.
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Francesca Day answered on 18 Mar 2014:
Stars are born from clouds of dust that collapse together through their own gravitational attraction. The star light comes from nuclear reactions taking place inside the star. When the star runs out of fuel for these nuclear reactions, it begins to die. How this process works depends on the size of the star, but generally the star explodes and then a cold dense core is left over. Sometimes the dying star turns into a black hole!
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Nick Wright answered on 18 Mar 2014:
Stars are born when giant clouds of gas build up in one place in space and then collapse because of their own gravity. This leads to a dense ball of material which is so dense and hot in the centre that nuclear reactions can take place and burn hydrogen into helium, which releases the energy that powers the star. When the star runs out of hydrogen it begins to die, passing through a number of short phases when it burns other nuclear fuels (like helium or carbon) and then eventually dying, either as a planetary nebula (if the star is small like our Sun) or as a supernova (if the star is much larger).
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Alan Fitzsimmons answered on 18 Mar 2014:
Stars are born from huge clouds of gas. These clouds collapse under gravity, their centres become hot enough to start nuclear reactions, and that’s how stars are born.
If you can find a star map and find the constellation of Orion when it gets dark, then you should be able to spot the orion nebula. In binoculars you can see its a cloud of gas. In large telescopes we can see that parts of the nebula are collapsing to form stars right now.
How a star dies depends on how big it is. A star like the Sun will die by growing into a red giant and throwing off its outer layers. This leaves behind its small hot core that we call a white dwarf star.
Stars much bigger than the Sun can die by exploding as a supernova. These explosions are as bright as a 100,000 million normal stars, and we can see them half way across the Universe!
If you can see Orion after sunset, one of the brightest stars is Betelgeuse (pronounced beetle-juice!). That will die by exploding as a supernova sometime in the next million years.
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