VIEW: Elements in Stars
Elements in Stars
All matter is made up of atoms -- elements comprised of smaller particles such as protons, neutrons, and electrons. The number of protons within the nucleus -- the central component of the atom -- determines the type of element.
The entire universe shares a common set of elements. In the very early universe, the only elements were hydrogen and helium. But since the formation of stars, lighter elements within the stars began fusing to create heavier elements, producing all the other naturally occurring elements. Under the extremely high temperatures and pressures within the core of stars, atoms collide, allowing nuclear fusion to occur.
All stars live by fusing hydrogen into helium.At even higher temperatures and pressures, heavier elements are able to form. Many are made from a process called "helium capture," in which a heavier element fuses with a helium atom. For example, helium fuses with carbon to make oxygen, and helium fuses with oxygen to make neon. Heavier nuclei can also fuse with each other, such as when carbon and oxygen fuse to make silicon or two silicon atoms fuse to make iron. Eventually, the interior of a massive star begins to resemble an onion, with different elements being created in different layers. However, elements heavier than iron are only produced in the extraordinary conditions created by the collapse and explosion of a star -- a supernova.
The creation of elements in the Big Bang has a direct effect on the elements within stars. Not surprisingly then, stars are largely made of up of hydrogen and helium. The exact numbers vary from star to star, but they are typically 73% hydrogen and 25% helium. That leaves 2% for other elements. The two most common "other" elements are carbon and oxygen. Older stars have heavier elements than younger stars.
The following video explains how elements are created in stars.
Sources
http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_mainsequence.html and Teachers' Domain, The Elements: Forged in Stars, published December 17, 2005, retrieved on July 14, 2010,
http://www.teachersdomain.org/resource/ess05.sci.ess.eiu.fusion/
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