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Unformatted text preview: Homework 7 NATS 102-13 26 April 2010 1. What is stellar parallax? What information does it provide? Stellar parallax is the 1/2 the angle the Earth appears to subtend in its orbit about the Sun as seen from a distant start. This is also 1/2 the angle the distant star appears to move with respect to the background stars as the Earth moves in its orbit about the Sun. This angle, combined with a little trigonometry provides the distance to the star. This is the rst step in the distance ladder and provides distances for nearby stars. 2. What does a stars luminosity measure? The luminosity of a star tells us its intrinsic energy pro- duction. Luminosity has units of ergs/s or joules/s (watts). The luminosity of an object is a combination of its temperature and its size. 3. Consider two identical stars, with one 5 times farther away than the other. How much brighter will the closer star appear than the more distant one? This the distance squared rule. If a star is 5 times further away, its brightness is 52 dimmer. So the closer star appears 25 x brighter than the further star. 4. How and why is the spectrum of a star related to its surface temperature?...
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