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10 Cards in this Set
- Front
- Back
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How is a star born?
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First, a molecular cloud must be formed. Then, the molecular cloud begins to collapse and gravity pulls the gas into dense regions causing the cloud to fragment into smaller pieces. After that, the cloud continues to contract until the central temperature begins to rise and is now a protostar. When the temperature of a protostar reaches 10 million K, hydrogen fusion can begin and the protostar becomes a true star.
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How are heavy elements manufactured by stellar nucleosynthesis?
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Each time a star's core has depleted an element its fusing, it shrinks and heats up until another element begins fusion. This starts off with hydrogen, then helium, then carbon, then oxygen, so on until iron.
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What is a supernovae and how does it contribute to the dispersal of heavy elements?
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A supernovae is the explosion of a high mass star when iron stops fusing and the core collapses. In a split second, the star then explodes because the collapse created such an immense amount of energy. This explosion disperses the heavy elements which are then collected by other forming stars and used in the cycle over again.
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What does it mean when it is said that we are all made of "star stuff?"
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This means that all the elements we find here on earth, including ourselves, are made up of remnants of exploded stars.
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What kind of nucleosynthesis occurs in main sequence?
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In a main sequence star, nucleosynthesis is process in which hydrogen is fused, and when all the hydrogen is fused, helium starts to fuse, and when all the helium is fused then carbon begins fusion. For a main sequence star, there is not enough temperature to continue the process and the star "dies" after all the carbon is fused.
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What kind of nucleosynthesis occurs in giant/super giant stars?
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Nucleosynthesis that occurs in giant/super giants stars happens beyond carbon fusion. Helium capture fuses helium with other nuclei creating carbon, fusing carbon into oxygen, oxygen into neon, etc. Once the core reaches iron fusion, it cannot fuse anymore.
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What type of important role does mass play in stellar evolution?
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High mass stars live "faster" and when they die they leave behind either a neutron star or a black hole. Low mass stars live "slower" and when they die they leave behind a white dwarf.
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What are the characteristics of a molecular cloud and how does it help a star to form?
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Molecular clouds are dense and cold. This allows hydrogen atoms to pair up to form hydrogen molecules. Also, these clouds are usually large because mass helps gravity overcome gas pressure. It helps stars to form because these things encourage the cloud to collapse.
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How is a protostar formed, and how is a main sequence star formed from a protostar?
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A protostar is formed when a molecular cloud collapses due to gravity. The growing density of these areas makes it difficult for radiation to escape. When the area is dense enough to prevent thermal radiation from leaving, then the central temperature and pressure begin to rise which causes a protostar.
A main sequence star forms when a protostar's core reaches 10 million K. |
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What is a protostar?
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A protostar is a clump of gas that will become and new star. Protostars have jets, which are high-speed streams of gas, protostellar winds whcih is an outward flow of particles. Jets and winds help dissipate the "cacoon" of gas surrounding the protostar, also causing the rotation to slow.
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