Ch17 - Assignment: Chapter 17 Class: Astronomy I Date:...

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Assignment: Chapter 17 Class: Astronomy I Date: October 29 th , 2007 Review Questions 1. Luminosity is how much energy they emit into space per second compared to that of the Sun. The actual brightness is not compared to the luminosity of the Sun. 2. Parallax method of finding a star’s distance is similar to the two points of view method. The direction from Earth to a nearby star changes as our planet orbits the Sun, and the nearby star appears to move back and forth against the background of more distant stars. 3. It takes a long time to use parallax method for finding a star because the stars are so far away, that they take much time to move their positions as seen from Earth. 4. All known stars have parallax angles less than one arcsecond. Therefore, these small parallax angles are difficult to detect. But measuring the parallax angles can tell scientists how far away the stars are from Earth. 5. The inverse-square law states that the apparent brightness of light that an observer can see or measure is inversely proportional to the square of the observer’s distance from the source. Since the light bulb is much closer to us than the stars, it appears brighter than a star. 6. To calculate the Sun’s luminosity, you need to know the distance of the Sun from Earth, as well as its apparent brightness in W/m 2 . 7.
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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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Ch17 - Assignment: Chapter 17 Class: Astronomy I Date:...

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