The Deaths of Stars - Part 1 of 2.pdf - Red Giants The...

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The Deaths of Stars – Part 1 of 2Red GiantsEventually, the nuclear fusion in the core of a "normal" star ends up consuming somuch of the hydrogen that the reaction rate slows down. Other nuclear fusionreactions then dominate and begin to spread out from the core, working their wayoutward in thin layers. This is calledhydrogen shell burning.As the source of heat moves out from the core, the entire star expands — a lot —and becomes a red giant. A red giant can be 400 billion metres in diameter — biggerthan Earth’s orbit. This makes the heat spread out more, so the outermost layer is alittle less hot than before. Eventually other, more complicated nuclear reactions takeplace and a red giant star displays drastic changes in size, colour and brightness.The last thing that happens to a red giant star is that most of its outer layers getexpelled in aplanetary nebula.White DwarfsWhat is left behind after a red giant expels most of its outer layers is a small starthat is very dense and hot. The most famous white dwarf star is the first one thatwas discovered, Sirius B. In 1862, astronomers did not know how to explain thistype of object, and it created a sensation among experts.Nuclear fusion no longer takes place inside a white dwarf, but the left over heat fromits days as a star keep a white dwarf hot for a very, very long time — astronomershave not found any white dwarfs that have cooled off. A white dwarf star that doeseventually cool off is called ablack dwarf, and of course, it would be really hard to

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Term
Fall
Professor
NoProfessor
Tags
Supernova, White dwarf, Neutron star, Red Giants

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