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PHYS 1040: Elementary Astronomy
Homework #2, Spring 2008
“We are a way for the Universe to know itself.” ∼Carl Sagan
1: Provide a topic or title for your semester project, and a short paragraph describing what interests you about this topic (or alternatively, a short paragraph describing what you want to learn about this topic). Topics should be astronomy based or related to astrophysical science. A list of possibly interesting ideas and topics is posted on the class website; inspiration might also be gained by thumbing through your textbook. If you are having trouble thinking of something, stop by and see me or drop me an email.
2: Taking Physics 1040 is going to pay off and make you a famous astrophysicist. While doing an observing project one night, you discover a new star in the Andromeda Galaxy^1 , which you promptly name after your instructor. If you know how far the star is from the center of the galaxy, describe how you can estimate the time it takes to make one full trip around the galaxy. [Hint: Remeber that Kepler’s Laws of Planetary Motion pertain to all orbits, not just planet orbits!]
(^1) In reality, the telescopes we use at Weber State don’t have the angular resolution to detect individual stars in the Andromeda Galaxy. Hubble discovered stars in M31 using the 100” telescope on Mount Wilson.
3: The Large Binocular Telescope (LBT) will be the largest telescope in the world when it is completed in late 2007, with a mirror diameter of D = 11.8 m. Estimate the size of the smallest object the LBT could see on the Moon. [Hint: A similar calculation to this was done for the Hubble Space Telescope in the lecture notes.]
4: Your mantra is the mantra of astronomy, “Sleep is for the weak!” You spend your nights out under the winter sky sweeping the sky with binoculars. One night you discover a comet, which they name after you^2. The comet doesn’t look very interesting however because it is moving directly along your line of sight, and simply looks like a round cloud of gas. It would be good to know if the comet is moving towards us, or away from us. Describe how we could determine this important and useful piece of information.
5: The star γ Andromedae (“gamma Andromeda”, also known as Almach) is a double star at the end of the constellation Andromeda which can easily be seen in a telescope. One of the stars has a blue-green color, and the other star has a yellow-orange color. Which star is likely the hotter star? Explain.
(^2) This is standard practice; most comets have been discovered by amateurs, like the recent Comet Holmes.
