lecture_tan30 - Key Concepts: Lecture 30: Galaxies...

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Key Concepts: Lecture 30: Galaxies Galaxy Types: Spirals, Ellipticals, Irregulars, Dwarfs Spiral Density Waves The Classification of Galaxies Galaxies can be classified by how they appear on the sky – How flattened the spheroid is – How prominent the disk and spiral arms are – If there is a bar Hubble devised what he thought may be an evolutionary sequence Elliptical Galaxies • Only a smooth spheroidal component • Hubble class subdivides them • E0 - circular • E7 - most elongated • No prominent disk • Composed of old reddish stars • Little dust, gas or ongoing star formation M87 - E0 E7 Spiral Galaxies Have disk with two or more arms – Bulge is old and red – Disk has gas and star formation Hubble sequence (Sa, Sb, Sc) – size of nuclear bulge vs. disk – tightness of spiral arms S0 or lenticular – Have disk but no arms Sb Sc
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M83 classed as SBb bar NGC 4565 - Edge on Sb
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This note was uploaded on 09/07/2011 for the course AST 1002 taught by Professor Dr.haywoodsmith,jr during the Spring '07 term at University of Florida.

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lecture_tan30 - Key Concepts: Lecture 30: Galaxies...

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