StudyGuide#2

StudyGuide#2 - (54 Two of the most easily recognizable...

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(54) Two of the most easily recognizable constellations that are up in the sky at this time of year are Leo and Orion. Find the following information about Leo and Orion: Approximate location in the evening sky this month, based on the star chart on page A-32 (rough altitude and azimuth), star chart (sketch of the pattern of the 6-8 brightest stars that make up the constellation), name of the two brightest stars, 2-3 sentence summary of the mythology behind the constellation. Remember the links: for mythology it is http://www.emufarm.org/~cmbell/myth/ myth.html . For simple star charts, it is http://www.dibonsmith.com/constel.htm (but I would prefer you use the back of your book star chart given above). For star names and other information, try http://www.astro.wisc.edu/~dolan/constellations/ . (TQ) (55) Stars are often classified according to their type with letters from A through O. The Sun, for example, is a G-type star. What was the original use of the ABCDEF. .. system? In other words, what distinguishes a type A from a type B from a type C star? Today, we usually sort stars into the sequence OBAFGKM. What is this sequence based on? Your book can help you answer this. (TQ) (56) The original stellar classification system was developed and later revised by Annie Cannon. One of her colleagues, Cecilia Payne-Gaposhkin, made an important discovery about the composition of stars. Describe the nature of her discovery (which, at the time, was not taken seriously even by her academic advisor). (TQ) (57) Explain why atoms like Hydrogen tend to have weaker absorption line strengths at very low temperatures and very high temperatures. In hotter temperatures atoms like Hydrogen are ionized, which does not allow them to absorb electrons. At lower temperatures the gas is not moving around enough to be excited and jump up energy levels. Both of these factors make for weak absorption lines. Correct. (58) If a star was very weak (or non-existent) Hydrogen lines, does that means the star has no Hydrogen? Explain. Also, how would we be able to tell whether the weak Hydrogen lines are due to high temperatures, low temperatures or simply a lack of Hydrogen? No, it does not necessarily mean that the star has no Hydrogen, although this is one of the possibilities. Other explanations could be that the star is very cool and
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can’t get enough energy to increase levels. We could figure out which of these explanations is correct by measuring the temperature another way. Using ionization species to determine the temperature would either show high temperature if there were high ionization species present or if conditions were ideal for Hydrogen lines we would know that the lack of lines is due to a lack of Hydrogen in the star. Correct. (59)
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This note was uploaded on 06/14/2008 for the course PHYS 20083 taught by Professor Ingram during the Spring '08 term at TCU.

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StudyGuide#2 - (54 Two of the most easily recognizable...

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