Ch18 - Assignment Chapter 18 Class Astronomy I Date...

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Assignment: Chapter 18 Class: Astronomy I Date: November 5 th , 2007 Review Questions 1. Astronomers have to piece together the evolutionary history of stars by studying different stars at different stages in their life cycles. 2. Stars last very much longer than the lifetime of any astronomer-indeed, far longer than the entire history of human civilization. Therefore, it is impossible to watch a single star go through its formation, evolution, and eventual demise. 3. Interstellar medium is just a combination of gas and dust. Stars appear very bright compared to the interstellar medium around them. 4. The evidence of dust and gas particles is apparent by seeing the dim appearances of the distant stars behind the interstellar medium. 5. The H II regions are found near hot, luminous stars of spectral types O and B. Such stars emit copious amounts of ultraviolet radiation. When atoms in the nearby interstellar gas absorb these energetic ultraviolet photons, the atoms become ionized. 6. As the two stars that make up a binary system orbit their common center of mass, their spectral lines shift back and forth. But certain calcium and sodium lines are found to remain at fixed wavelengths. These stationary absorption lines are therefore not associated with the binary star. 7. A dark nebula is so opaque that it blocks any visible light coming from stars that lie behind it. 8. The light from remote stars is also reddened as it passes through the interstellar medium, because the blue component of their starlight is scattered and absorbed by interstellar dust. This same effect makes the Sun look red, the sky look blue, and the mountains look purple. 9.
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This note was uploaded on 08/25/2008 for the course ASTRON 1 taught by Professor Jsepikas during the Winter '07 term at Pasadena City College.

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Ch18 - Assignment Chapter 18 Class Astronomy I Date...

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