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Unformatted text preview: Homework #5 1)How does interstellar dust affect our observation of the Stars and the Milky Way? (Q.Rev. #3 pg. 593) Interstellar dust causes extinction in shorter wavelengths (visible) and hence the Milky Way is best studied in the longer wavelengths – mainly in the radio and the infrared. Stars appear to be reddened and dimmed when viewed through dust mainly due to scattering and absorption being more efficient at shorter wavelengths. Thin clouds of dust close to stars reflect the scattered light toward our direction causing the appearance of a Reflection Nebula. Visibly we can only see the nearby parts of our galaxy. 2) What evidence makes astronomers believe that the Milky Way has spiral arms? (Q.Rev. #4 pg. 593) Since the observation of the Milky Way is limited by the presence of dust at the shorter wavelengths, the Milky way is studied in the radio and infrared parts of the spectrum where extinction due to dust is relatively low . Observations of cool hydrogen regions which generally lie along the spiral arms, in the relatively low ....
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This note was uploaded on 05/18/2008 for the course ASTR 101 taught by Professor Deming during the Spring '07 term at Maryland.
- Spring '07
- The Milky Way