lecture18

lecture18 - Astronomy 3 The Nature of the Universe...

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Astronomy 3: The Nature of the Universe Professor Alice Shapley Lecture 18: Cosmology (NGC 1499 Image credit: Markus Noller, Deep Sky Images)
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Logistics Final exam: Monday, June 6 th , 11:30 am – 2:30 pm. Location: Fowler A103B. Most important : bring a #2 (i.e. normal) pencil. Recommended: bring a calculator. Scantrons will be provided. Review session for final exam: – This Thursday, June 2 nd , 6-8 pm. Location: MS 4000A (i.e. lecture hall). Sheet of useful formula and numbers will be provided along with final exam.
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Logistics Exam will have a mixture of multiple choice, matching, and true/ false, and will contain 90 questions, worth 1 point each. Exam will emphasize material on Measurements of Stars, Stellar Life Cycles, Stellar Remnants, Black holes, The Milky Way, Galaxies, Cosmology. This new material corresponds to lectures 12-18. The relevant reading from the textbook is: Chapters 15, 16, 17, 18, 19, 20, 22. There will also be material from the first part of the class on the exam, corresponding to Lectures 1-11, and Chapters 1-11, 13, 14. A few questions will be based on Labs.
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Review from Last Time The Milky Way Galaxy: major components, motions, dark matter. The Galactic Center: black hole! Galaxy types.
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Edge-on, our galaxy looks like a flattened “disk” of stars with a central concentration or “bulge” of stars. Note the location of the Sun, very far from the Center. The disk is 1,000 light-years thick but 100x that in width – very thin! • Primary features: disk, bulge, halo, globular clusters. • Useful distance unit for Milky Way: kiloparsec (kpc) = 1000 parsecs ~3000 light years.
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Orbital motions in the Milky Way Sun’s orbital period 250 million years v rot =220 km/s Disk has differential rotation. 1. Disk: Nearly circular rotation 2. Halo: Random, elliptical
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Deriving Mass of the Galaxy from its ( non-Keplerian ) Rotation Only interior mass affects rotation. (Like our solar system)
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Dark Matter Most of the mass in the Milky Way galaxy: – Does not radiate – Is not ordinary “baryonic” matter, such as protons, neutrons, electrons On bigger scales (clusters of galaxies) dark matter fraction even higher. – Over 80% of matter is dark
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What lies at the center of our Milky Way Galaxy? In the direction of the constellation Sagittarius, our Galactic Center hosts a supermassive black hole (~4x10 6 M sun ). We can weigh the black hole at the Galactic Center by following the orbits of stars in its vicinity and using Newton/Kepler’s laws to infer how much mass must be there. One of the most convincing pieces of observational evidence for a black hole! Note: separate from issue of
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This note was uploaded on 10/28/2011 for the course ASTR 3 taught by Professor Hauser during the Spring '07 term at UCLA.

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lecture18 - Astronomy 3 The Nature of the Universe...

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