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Unformatted text preview: rotating gas. This galaxy rotation problem is thought to be explained by the presence of large quantities of unseen dark matter .   Beginning in the 1990s, the Hubble Space Telescope yielded improved observations. Among other things, it established that the missing dark matter in our galaxy cannot solely consist of inherently faint and small stars.  The Hubble Deep Field , an extremely long exposure of a relatively empty part of the sky, provided evidence that there are about 125 billion (1.2510 11 ) galaxies in the universe.  Improved technology in detecting the spectra invisible to humans (radio telescopes, infrared cameras, and x-ray telescopes ) allow detection of other galaxies that are not detected by Hubble. Particularly, galaxy surveys in the Zone of Avoidance (the region of the sky blocked by the Milky Way) have revealed a number of new galaxies...
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- Fall '10