galaxies - Galaxies Galaxies First spiral nebula found in...

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1 Galaxies Galaxies First spiral nebula found in 1845 by the Earl of Rosse. Speculated it was beyond our Galaxy. 1920 - "Great Debate" between Shapley and Curtis on whether spiral nebulae were galaxies beyond our own. Settled in 1924 when Edwin Hubble observed individual stars in spiral nebulae. Sample of Galaxies Spiral Barred Spiral Irregular Dwarf Elliptical A bar is a pattern too, like a spiral Milky Way schematic showing bar A barred spiral galaxy Galaxy Classification Spirals Ellipticals Irregulars barred unbarred E0 - E7 Irr I Irr II SBa-SBc Sa-Sc "misshapen truly spirals" irregular First classified by Hubble in 1924 => "tuning fork diagram" bulge less prominent, arms more loosely wrapped Irr disk and large bulge, but no spiral increasing apparent flatness Still used today. We talk of a galaxy's "Hubble type" Milky Way is an SBbc, between SBb and SBc. Later shown to be related to other galaxy structural properties and galaxy evolution. Ignores some notable features, e.g. viewing angle for ellipticals, number of spiral arms for spirals. bulge less prominent, arms more loosely wrapped Irr disk and large bulge, but no spiral increasing apparent flatness
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2 The Variety of Galaxy Morphologies http://galaxyzoo.org/ a) elliptical b) spiral c) barred spiral d) dwarf e) irregular 1 2 3 4 5 Clicker Question: What type of galaxy do we live in? A: Elliptical B: Dwarf Elliptical C: Spiral D: Irregular Clicker Question: What type of galaxy is the Large Magellanic Cloud? A: Elliptical B: Dwarf Elliptical C: Spiral D: Irregular Irr I vs. Irr II Irr I (“misshapen spirals”) Irr II (truly irregular) Large Magellanic Cloud Small Magellanic Cloud These are both companion galaxies of the Milky Way. bar poor beginnings of spiral arms Ellipticals are similar to halos of spirals, but generally larger, with many more stars. Stellar orbits are like halo star orbits in spirals. Stars in ellipticals also very old, like halo stars.
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galaxies - Galaxies Galaxies First spiral nebula found in...

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