Homework 13 Due Friday, April 2, 2004

  1. Kapteyn's star, named after the Dutch astronomer who found it, has a parallax angle of 0.255 arcsec. How far away is the star?

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  2. If a red star and a blue star both have the same radius and both are the same distance from the Earth, which one looks brighter in the night sky? Explain why.

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  3. What are the most prominent absorption lines you would expect to find in the spectrum of a star with a surface temperature of (a) 35,000 K, (b) 2800 K, and (c) 5800 K (like the Sun)? Briefly describe why these stars have such different spectra even though they have essentially the same chemical composition.

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  4. Suppose that you want to determine the temperature, diameter, and luminosity of an isolated star (not a member of a binary system). Which of these physical quantities require you to know the distance to the star? Explain.

     

  5. How much dimmer does the Sun appear from Neptune than from Earth?