Galaxies Button for link to Chinese version of this page
Galaxy Formation. Galaxy formation began about 13 to 13.2 billion years ago, and has been a long process, with galaxies such as the Milky Way reaching something like their current shape and size about 9 to 10 million years ago. Hubble Space Telescope deep space images show galaxies looking rather mature just a couple billion years after the big bang (approximately 11 billion years ago). Galaxies are not uniformly distributed around the universe. They seem to be clustered in sheets or strings, and there are great voids in the universe lacking galaxies. Galaxies vary in size, with some having only a few hundreds of thousands of stars, while others (such as the Milky Way) have trillions of stars. Many galaxes are about 100,000 light years across.

Links about galaxies:
  1. A serious science page of links about galaxy formation from the Astronomy Department at University of Texas at Austin (the Intergalactic Medium Research Group).
  2. James Schombert has provided a fine page of lecture notes for a lower-division astronomy course with ideas about the evolution of the universe.
  3. A simulation of a realistic galaxy at a page that discusses galaxy evolution.
  4. A fine page about galaxies.
  5. Another great page about galaxies, at Cambridge University.

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This work by Eric & Chun-Chih Hadley-Ives is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.