Transcript Stars - Brown

Stars
Life cycles and Nuclear Fusion
Taylor Wilson
How are they born?
• Stars born within nebulae
– Orion Nebula
• Knots arise as dust particles collect
– Collapse
• When nuclear fusion begins, a star is “born”
Nuclear Fusion
• Core is environment of extreme pressure and
temperature
– 15 million K
• Counteracts forces of gravitational attraction
• Fuses together lighter elements to create
heavier ones at core
• Exothermic process
• Energy released in the form of gamma rays
More on Fusion
Remember Newton’s 3rd Law?...
Deuterium and
Tritium are both
isotopes of
hydrogen.
Deuterium is stable
while Tritium is
slightly radioactive.
Maday! We’re out of hydrogen…
• Star leaves main sequence
• The most massive of stars can fuse other
elements (helium-iron) when deprived of
hydrogen
• Red giant 
• Next size determines the star’s fate
The Cycle Continues
• The mass lost by the star (supernova or shedding outermost
layers), in turn gathers elsewhere in the universe to create
new stars!
Bibliography
• Cain, Fraser. "Nuclear Fusion in Stars."
Universe Today RSS. N.p., 12 Feb. 2009. Web.
07 July 2014.
• Choi, Charles Q. "Stars: Formation,
Classification and Constellations." Space.com.
Purch, 15 Nov. 2010. Web. 05 July 2014.
• "Stars - NASA Science." Stars - NASA Science.
NASA, n.d. Web. 07 July 2014.