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# Photoelectric_Photometry_Answer_Sheet_02-23-10 - 6 Is this...

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Name __________________________________ Date______________________ Partner’s names__________________________ Section____________________ ________________________________________ Photoelectric Photometry of the Pleiades Part I: Record your values on the spreadsheet for this lab. Copy and paste your data table here. Part II: 1. Define absolute magnitude. 2. If m = M for a given star, how far would that star be from Earth? Use the formula d = 10 x 10 (m-M)/5 . Show your work. 3. What would it tell you about the distance if m was greater than M? 4. Remember that in this lab we are using v for apparent magnitude and V for absolute magnitude. What does it mean (in terms of distance) if your set of stars has apparent magnitudes (v) less than corresponding stars on the H-R diagram of known absolute magnitude (V)?

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5. Where do the main sequence stars in this cluster lie with respect to the main sequence of stars of known absolute magnitude?
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Unformatted text preview: 6. Is this cluster closer or farther than 10 parsecs away? 7. Using the graph and the distance equation, figure out how far away the cluster is in parsecs. Explain how you did it and show your work and the answer below. In 1958, H.L. Johnson and R.I. Mitchell calculated the distance to this cluster to about 410 light-years. As a percentage, how does your calculated value compare? Show your work. 8. Do any of your stars seem to lie in the red giant part of the H-R diagram? If so, identify them by their RA and declination. Copy and paste in a plot of the H-R diagram with your stars and the standard stars clearly identified here. Attach this answer sheet and a copy of the spreadsheet to the Blackboard submission box. Conclusion question (Individual work): Compare this method of finding distance to the method of parallax. Identify strengths and weaknesses of this method and explain assumptions we have made....
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