Photoelectric_Photometry_pre-lab_02-23-10 - Photoelectric...

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Photoelectric Photometry of the Pleiades Pre-lab A big question when looking at the stars is whether a bright star is a really close star that may not be that intrinsically bright, or a star quite far away that is also exceedingly bright. You know about stellar spectra and how they can serve as “fingerprints” for stars, telling about conditions in the star and the star’s temperature. You have examined a way of ordering stars in the H-R diagram where the spectral classification is related to the magnitude of the star, its luminosity. We now add in one more thing, the distance away of some stars that are close enough to measure with parallax (these days powerful telescopes, including the Hubble can be used to measure parallax for a large number of stars and to refine older measurements). Given the distances and magnitudes we can find absolute magnitudes for these stars and use them to devise an H-R diagram of stars that will serve as a “ruler” for other stars. Another very interesting bit of information to remember in this lab is that stars often form in large groups within a gas cloud. You can follow this link to see a forming cluster as viewed by the Spitzer and Chandra space telescopes. Because these star clusters form in a relatively small area, it is safe to assume that they are all approximately the same distance away. Because stars of different mass have different life times, with more massive stars around for
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This note was uploaded on 02/06/2011 for the course ASTR 114 taught by Professor Staff during the Spring '08 term at George Mason.

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Photoelectric_Photometry_pre-lab_02-23-10 - Photoelectric...

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