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Unformatted text preview: Astronomy 10, Fall 2008 Homework 11 - 40 points total Due in the boxes in the basement of Campbell Hall by 5pm Tuesday, December 2 . Be sure to include your name, SID, Section Number, and GSI name on your homework, and staple it together. 1. Galactic Differences (8 points) Below are images of two galaxies: the Andromeda Galaxy and Virgo A. Both are roughly equal in overall size and mass, but even with a quick glance they are obviously far from being the same. (Note that youll want to use the full color images for this problem, so look off the PDF file if you cant print it out in color.) (a) What are the Hubble types of these galaxies? (Hint: see slides 18 and 19 in lecture 21, or figure 20.8 in the book, or http://upload.wikimedia.org/wikipedia/en/2/21/HubbleTuningFork.jpg for examples to compare to.) (2 points) (b) Based on their appearance in the images, which of the two galaxies has more gas and dust? How can you tell? (2 points) (c) Based on their appearance in the images, which of the two galaxies has more relatively old stars? How can you tell? (2 points) (d) Which of the two galaxies has more current star formation? How do your previous answers tell you this? (2 points) 2. The Mass of a Gravitational Lens (6 points) Below is an image of a large cluster of galaxies (note that the image is inverted so that dark areas in the images is where the light is coming from). Nearly every dot and fuzzy blob in this image are all separate galaxies in the cluster. But very elongated arcs can also be seen (some of which, but not all, are indicated). These arcs are images of galaxies much farther away behind the cluster that have been distorted by the gravitational pull of the mass in the galaxy cluster. (a) With your ever-trusty telescope, you observe a type Ia supernova (which had a peak luminosity of L = 5 10 9 L ) in one of the galaxies of the cluster. If you measure the apparent brightness) in one of the galaxies of the cluster....
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