2.23 Astro 1 Section 1 Professor Brandt

2.23 Astro 1 Section 1 Professor Brandt - Astro 1 Section 1...

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Astro 1 Section 1 Professor Brandt Wednesday February 23rd 1999 Announcements: Lecture notes: Class 20 Now that we've gone through all the needed terminology and background we can start talking about how people first worked out the size and shape of our Galaxy. One of the first methods people used was to count stars in various directions. William Herschel in 1785 - Milky Way map. proposed disk of stars. 4x longer than thick - we are at center. Jacobus Kapetyn - spent 40 years counting stars on photographic plates. 1920- 22 said that disklike shape with sun near center. But unfortunately both Herschel and Kapetyn models for the Galaxy were drastically wrong. There was a problem they did not properly understand. Space contains obscuring dust that makes it so that we cannot see stars throughout our Galaxy. Dust makes a star's light fainter. Also blue light is absorbed more than red light so dust makes a star look redder. Since Herschel and Kapetyn could not properly see all the stars they could not properly map the Milky Way.
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  • Spring '99
  • Brandt
  • Astronomy, Harlow Shapley, globular clusters

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