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The Question

(Submitted November 27, 2002)

The Hubble Space Telescope (HST) site estimates there are hundreds of billions of galaxies in the universe. A recent German super-computer simulation estimates that the number may be as high as 500 billion! Can someone please clarify the accepted educated ballpark figure? Thanks a billion!

The Answer

Your inquiry is definitely in the minds of many scientists who are trying to obtain a good estimate for the number of galaxies in the universe. The methods used to achieve such number varies, and therefore, the results would vary, too. Also, as new and improved technology becomes available, astronomers can detect fainter objects that were not seen before. These objects that have come into view will in turn change the estimated number of galaxies.

For example, in 1999 the Hubble Space Telescope estimated that there were 125 billion galaxies in the universe, and recently with the new camera HST has observed 3,000 visible galaxies, which is twice as much as they observed before with the old camera. We're emphasizing "visible" because observations with radio telescopes, infrared cameras, x-ray cameras, etc. would detect other galaxies that are not detected by Hubble. As observations keep on going and astronomers explore more of our universe, the number of galaxies detected will increase. For more about the Hubble Space Telescope, check out this web site:

Hope this helps,
Georgia & Veronica
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