The Life Cycle of a Star

The Life Cycle of Star compared to a Humans

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First Stage: Nebula/Protostar

The nebula is the birthplace of a star. A nebula is a cloud of dust and gas located in the interstellar medium. The interstellar medium is everywhere in space. It consists of about 97% Hydrogen and 3% Helium. In the Nebula there are different regions where gravity causes dust and gas to join together forming "clumps". When these “clumps” gather more atoms, their gravitational pull towards other atoms increases, pulling more and more atoms into the “clump.” This clump is known as protostar, this is the birth of the star. In order for a protostar to become a real star, it will need to achieve and maintain equilibrium between the pressure and the gravity. A star remains in the Protostar phase for a very short time.
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The Main Sequence

The Main Sequence is the where a star spends majority of its life. During the Main Sequence the star is fusing Hydrogen into Helium in the core (nuclear fusion). The length the star is in the Main Sequence for depends on its size. A small star will never reach the main sequence. A Low size star will be in it for 54 billion years, a medium star for 43 billion years, and a massive star for 31 billion years. As soon as all of the hydrogen fuel is gone the star leaves the Main Sequence Stage.


In the photo below, it is our Sun in the Main Sequence

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Red Giant

During the Red Giant stage, Helium is now being burned in the core. A red giant is larger then a star during the Main Sequence stage but is less stable. The outside surface of this star is much cooler then during the Main Sequence
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Different Deaths of a Star

The size of the star or the mass determines the way that a star dies. There are several different ways it can die, which is shown in the pictures below.

The Role of a Stars Light

A stars light will reveal the composition of the star. Red-shifted means, "Since red is at the low-frequency end of the visible spectrum, we say that light from a receding star is shifted toward red, or red-shifted." In a red shift the wavelength is being lengthened Blue-shifted means, "Since blue is at the high-frequency end of the visible spectrum, we say the light from an approaching star is shifted toward blue, or blue-shifted." In a blue shift the wave length is being shortened.

Where do the elements come from?

The stellar nucleosynthesis theory is how elements are formed. From this theory we can understand why some elements like carbon, oxygen, silicon, and iron are quite common while the heavier elements such as gold, mercury, and uranium are so rare. The lower mass stars can only create helium. Stars like our sun can create the elements, helium, carbon, and oxygen. Massive stars can create helium, carbon, oxygen, neon, magnesium, silicon, sulfur, argon, calcium, titanium, nickel, chromium, and iron. Elements that are heavier than iron are made in a supernova explosions from the, "rapid combination of the abundant neutrons with heavy nuclei." Massive red giants can make small amounts of elements heavier than iron (as large as mercury and lead) through a slower combination of neutrons with heavy nuclei. However a supernova generates the majority of elements that are heavier then iron.

Bibliography

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"Origins: Hubble: Tools: Doppler Effect & Redshift | Exploratorium." Exploratorium: The Museum of Science, Art and Human Perception. N.p., n.d. Web. 22 Mar. 2015. <http://www.exploratorium.edu/hubble/tools/doppler.html>.

"Protostars." Protostars. N.p., n.d. Web. 23 Mar. 2015. <http://aspire.cosmic-ray.org/Labs/StarLife/starlife_proto.html>.