hw9_solutions - Homework #9: Solutions Astro 10, spring...

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Unformatted text preview: Homework #9: Solutions Astro 10, spring 2010 General Notes to Graders: If numerical answers are roughly correct, do not take marks off. Award part marks if the student has made some progress with the question. Be generous. 1. [5 points] Supernovae are important for the formation of planets and life because they provide the only way to produce heavy elements and distribute elements through the cosmos . You’ve learned in class that most of the universe is hydrogen, with a little helium on the side. But we don’t see this on Earth - there is water, rocks, copper, iron, life, etc. These ”heavier” el- ements like carbon and oxygen and nitrogen are by products of later stages of nuclear fusion in stars. But those by products need a way to get out of the star and go someplace else (and eventually form another star and planets). The best way to do this is with supernovae explo- sions which launch this stellar material back into the cosmos, mixing together and eventually reforming into more stars. Also, elements heavier than iron MUST be produced in supernovae explosions - regular stars do not have the necessary energy to make anything heavier than iron. The fact that Earth has lots of carbon, oxygen, nitrogen, as well as some natural uranium present strongly suggests that a supernova explosion occurred in the distant past in our galactic neigh- bourhood. The Sun and the planets were then formed out of this stellar debris. Notes to graders: Students should have a discussion equivalent to this in content to receive full credit. 2. [20 points] a) If you assume that all stars in a cluster were formed at the same time, then the second cluster is the older one. Why? Because it has no O, B, A stars left. These massive and luminousis the older one....
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This note was uploaded on 07/18/2011 for the course ASTRO 10 taught by Professor Norm during the Spring '06 term at Berkeley.

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hw9_solutions - Homework #9: Solutions Astro 10, spring...

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