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Normal Galaxies
Galaxies are gravitationally-bound systems of stars, gas, dust and dark matter. A typical large spiral galaxy such as our home galaxy, the Milky Way, consists of hundreds of billions of stars, enough gas and dust to make billions more stars, and at least ten times as much dark matter as all the stars and gas put together.
In the 1920s, Edwin Hubble used the 100-inch optical telescope on Mount Wilson, in California, to find other galactic systems. NASA's Hubble Space Telescope, named in Hubble's honor, has observed billions of galaxies of different sizes and shapes. There are irregular small dwarf galaxies, majestic spiral galaxies, and elliptical galaxies ranging in size from dwarfs to supergiants ten times larger than the Milky Way galaxy.
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