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Unformatted text preview: SIO 35: Midterm Study Guide 1. What is fusion and what is required for fusion to occur? In your answer explain how He is formed from H. How is fusion different from fission? Fusion is when two or more nuclei fuse together to make a heavier, single atom. Large amounts of energy/heat required. The fusion process powers the stars, where foour atoms of H form an atom of He. By contrast, Fission is the process by which a heavier nucleus splits into smaller nuclei, with the release of energy. 2. Explain why the abundance of Fe is anomalously high. The abundance of Iron (Fe) is anomalously high for its atomic weight because Fe is the last element that can be made by fusion in a star. All the elements above Fe release energy are made it in a supernova as their abundances cascade down. But Fe is the last because it releases more energy than it requires for fusion. Because of this, its abundance is anomalously high. 3. Discuss the life cycle of a star (small and massive). The star begins as a cool cloud of gas and begins to collapse under its own gravity. As it collapses, it gets hotter and hotter as its gravitational energy is released as radiation. The core eventually gets hot enough to begin the burning of hydrogen. The energy keeps the star from collapsing further but eventually the hydrogen will run out. The star collapses again as its outer regions are pushed outwards, in a stage called the Red Giant Stage. If the star is small, its life may end here creating a planetary nebula out of its atmosphere and a white dwarf from its core. A Massive star will collapse again and go through the sequence with the next elements (each time quicker), until it is ready to burn iron. But iron is the last element able to be by formed by fusion because it releases more energy than it consumes to fuse. Because of this, fusion stops and the star will implode, creating a supernova. 4. Name three other places we believe water exists in our universe besides earth and discuss the evidence (be specific). Mars evidence of frozen ice caps, ripple marks that indicate bed forms where water might have been, and found salt deposits that result from evaporation, suggesting water might have been here Europa (moon of Jupiter) photographs show surface that is with many fissures, as if it is made of ice that freezes and thaws repeatedly. It may have been a frozen ball of ice before. Moon water-ice found in craters that were never exposed to Sunlight 5. What is the best estimate for the age of the universe? What is best estimate for the age of the What is the best estimate for the age of the universe?...
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This note was uploaded on 09/06/2011 for the course SIO 35 taught by Professor Driscoll,n during the Winter '08 term at UCSD.
- Winter '08