Chapter 16

Chapter 16 - Note that the following lectures include...

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Note that the following lectures include animations and PowerPoint effects such as fly ins and transitions that require you to be in PowerPoint's Slide Show mode (presentation mode).
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Galaxies Chapter 16
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The preceding chapter was about our Milky Way Galaxy, an important object to us but only one of the many billions of galaxies visible in the sky. We can no more understand galaxies by understanding a single example, the Milky Way, than we could understand humanity by understanding a single person. This chapter expands our horizon to discuss the different kinds of galaxies and their complex histories. We take two lessons from this chapter. First, galaxies are not solitary beasts; they collide and interact with each other. Second, most of the matter in the universe is invisible. The galaxies we see are only the tip of a cosmic iceberg. We will carry the lessons of this chapter into the next, where we will discuss violently active galaxies, and on into Chapter 18, where we discuss the universe as a whole. Guidepost
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I. The Family of Galaxies A. The Discovery of Galaxies B. The Shapes of Galaxies C. How Many Galaxies? II. Measuring the Properties of Galaxies A. Distance B. The Hubble Law C. Diameter and Luminosity D. Mass E. Supermassive Black Holes in Galaxies F. Dark Matter in Galaxies Outline
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III. The Evolution of Galaxies A. Clusters of Galaxies B. Colliding Galaxies C. The Origin and Evolution of Galaxies D. The Farthest Galaxies Outline (continued)
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Galaxies Star systems like our Milky Way Contain a few thousand to tens of billions of stars. Large variety of shapes and sizes
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Galaxy Diversity The Hubble Deep Field: 10-day exposure on an apparently empty field in the sky Even seemingly empty regions of the sky contain thousands of very faint, very distant galaxies Large variety of galaxy morphologies: Spirals Ellipticals Irregular (some interacting)
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Galaxy Classification Sa Sb Sc E0 = Spherical Small nucleus; loosely wound arms E1 E6 E0, …, E7 Large nucleus; tightly wound arms E7 = Highly elliptical
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Gas and Dust in Galaxies Spirals are rich in gas and dust Ellipticals are almost devoid of gas and dust Galaxies with disk and bulge, but no dust are termed S0
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Barred Spirals Some spirals show a pronounced bar structure in the center They are termed barred spiral galaxies Sequence: SBa, …, SBc, analogous to regular spirals
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Irregular Galaxies Often: result of galaxy collisions / mergers Often: Very active star formation (“Starburst galaxies”) Some: Small (“dwarf galaxies”) satellites of larger galaxies (e.g., Magellanic Clouds) Large Magellanic Cloud NGC 4038/4039 The Cocoon Galaxy
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Galaxy Types (SLIDESHOW MODE ONLY)
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Distance Measurements to Other Galaxies (1) a) Cepheid Method: Using Period – Luminosity relation for classical Cepheids: Measure Cepheid’s Period Find its luminosity Compare to apparent magnitude Find its distance b) Type Ia Supernovae (collapse of an accreting white dwarf in a binary system):
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This note was uploaded on 11/04/2011 for the course PHYS 227 taught by Professor Professorroberts during the Fall '11 term at BYU.

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Chapter 16 - Note that the following lectures include...

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