chap 13 new-v3

chap 13 new-v3 - Galaxies Star systems like our Milky Way...

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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 • as well as varying amounts of gas and dust
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Galaxy Classification Sa Sb Sc Elliptical Galaxies Spiral Galaxies E0 = Spherical Small nucleus; loosely wound arms E1 E6 E0, …, E7 Large nucleus; tightly wound arms E7 = Highly elliptical
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Barred Spirals Some spirals show a pronounced bar structure in the center. They are termed barred spirals: 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 Sizes and Luminosities Vastly different sizes and luminosities: From small, low- luminosity irregular galaxies (much smaller and less luminous than the Milky Way) to giant ellipticals and large spirals, a few times the Milky Way’s size and luminosity
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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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Distance Measurements to Other Galaxies (I) a) Cepheid method: Using period – Luminosity relation for classical Cepheids: Measure Cepheid’s period Find its luminosity
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This note was uploaded on 04/25/2008 for the course PHY 122 taught by Professor Bernstein during the Spring '08 term at SUNY Buffalo.

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chap 13 new-v3 - Galaxies Star systems like our Milky Way...

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