AST-L22-ch15__3

AST-L22-ch15__3 - 1 Exam #3 postview Exams available at...

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Unformatted text preview: 1 Exam #3 postview Exams available at back of room Exam average was a 18.80 /30 or 62.8 % somewhat lower than previous tests (avg ~70%) But it was a harder test, and therefore gets a more generous curve . Well go over the test today in class Two separate keys ; Ill try to show you both (sort of). Galaxies 1: Milky Way 1) Exam postview 2) History 3) The Milky Way Galaxy 4) Introduction to Galaxies Todays Lecture: purpose & goals AST 1002 Planets, Stars and Galaxies Looking at the Milky Way Viewed as a bright band of stars across the sky called via lactia (latin) or galaxias kuklos (greek) Milky Way Telescopes revealed it composed of many distant stars Galactic center appears in the southern part of the sky (from the northern hemisphere) in constellation Sagittarius Much of the Milky Way is blocked visually by dust dark band through the middle of the Milky Way But we can study it using longer wavelengths e.g. radio waves, infrared penetrate the dust 2 The Milky Way in Visible Light Almost everything we see in the sky is our galaxy Most individual visible stars seen with the naked eye are foreground stars within a few hundred light years of us. Andromeda Galaxy The exceptions: Milky Way: Structure Disk Near the Sun the average density of stars is about 1 star per 330 330 cubic light years. Bulge In the galactic nucleus there are about 10 10 million million stars per cubic light year. Halo The globular clusters and many individual widely separated older stars form a halo about the galaxy. Milky Way: Structure II Characteristics Diameter About 100,000 l.y. The Sun is ~ 27,000 l.y. from the center and takes about 240 million years to make a complete orbit, at about 220 km/s . Age From the oldest stars we know that the galaxy is ~13-14 billion years old. Luminous Mass Between 100 to 500 billion solar masses. 3 Stellar Populations Population I Relatively rich in heavier elements (about 3% by mass) because they are of the second or third generation....
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This note was uploaded on 10/13/2011 for the course AST 1002 taught by Professor Gerstein during the Spring '08 term at FSU.

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AST-L22-ch15__3 - 1 Exam #3 postview Exams available at...

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