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Counting stars in the sky

  1. Jun 18, 2010 #1
    I want to know how astronomers count the number of stars (or any other celestial object for that matter) in the sky.

    Will they take a photograph and do some signal processing like counting the number of brightest spots? Is it possible to count accurately since there are billions and billions of stars. Or only a rough estimate based on some equation or theory is available to do that job?

    I am not related to this field but just want to know, whether there is any scope for application of signal processing techniques.
  2. jcsd
  3. Jun 18, 2010 #2


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    Simply counting visible stars by brute force doesn't work all that well. If you look at deep-sky photographs of the night sky, you'll see that many areas of our night sky are obscured by intergalactic materials, including heavy dust clouds. It's possible to detect some stars in back of such obscurations by "looking" in the far-infrared or perhaps in radio frequencies. Still, estimates of the total number of stars in the MW are just that - estimates based on extrapolations from observations.

    In bodies that are not dusty (globular clusters, for instance), one can infer stellar mass averages from spectroscopy, and estimate the stellar population from the luminosity of the body, with distances calculated from redshift measurements. There are many ways of skinning this cat.
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