PHYS 190 Chapter Notes - Chapter 9: Radio Galaxy, Before Present, Local Group
22 Mar 2018
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Document Summary
Astronomers classify galaxies according to various properties. Classification according to shape was developed by edwin hubble. There are galaxies w/ no disk, no spiral arms, almost no gas, dust, or new stars forming. Range in size & mass from small dwarfs to huge giants. Disk-shaped galaxies usually have spiral arms & generally large amounts of gas. Some galaxies have irregular shape, w/ gas, dust, star-forming nebulae. Large magellanic cloud - larger of 2 irregular galaxies visible in southern sky passing near milky way galaxy. Small magellanic cloud - smaller of 2 irregular galaxies visible in southern sky passing near milky way galaxy. Diff kinds of galaxies have diff colours depending mostly on how much star formation happening in them. Spirals & irregulars usually contain plenty of young stars, including massive, hot, luminous o & b stars. O & b stars produce most of light & give spirals & irregulars distinct blue tint. Elliptical galaxies usually have few young stars.
