Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Stargazing How can the telescopes take photos of distant galaxies?

  1. Oct 12, 2016 #1
    So how can the photos of distant galaxies have no nearer stars in front of them? Or photos of nebulae?
    I feel like there are so many stars.that it would be impossible to take a photo of a distant object without a star in front of the photo blocking the way. Or is it luck that there are no stars between here and the photos they took?
    What about photos of the deep space? Why is there no close star that is too close and takes up the shot in front of the millions of stars in the photo?
     
  2. jcsd
  3. Oct 12, 2016 #2

    1oldman2

    User Avatar
    Gold Member

  4. Oct 12, 2016 #3

    Drakkith

    User Avatar

    Staff: Mentor

    They often do. But individual stars are essentially impossible to see unless they are VERY large and VERY bright. Such stars only form a small percentage of the stars in the Milky Way. Nebulas are also very difficult to see unless they are very close or very large and bright.

    In addition, stars are really, really small compared to the ginormous distance between them. At a distance of one light year, a star with the same diameter as the Sun is only 0.0085 degrees across. At 4 light years, just about the distance to the nearest star, it would only be 0.002 degrees across. The chances that a ray of light leaves a source and impacts a star is extremely small.
     
  5. Oct 12, 2016 #4

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Most observable galaxies lay outside the galactic plane where most stars in the MW reside. Intergalactic space is mostly devoid of stars.
     
  6. Oct 12, 2016 #5

    davenn

    User Avatar
    Science Advisor
    Gold Member

    you are working from a very poor assumption

    indeed .... VERY often do ... there would be very few photos of objects internal or external to
    the Milky Way that don't show foreground stars

    sorry, have to strongly disagree with that.... they will be of all sorts of sizes and luminosities eg

    opo0833a.jpg

    ALL the stars in that image ( other than a tiny few very bright stars in that "larger galaxy) are foreground stars that are within the Milky Way


    Dave
     
  7. Oct 12, 2016 #6

    Drakkith

    User Avatar

    Staff: Mentor

    I'll tentatively agree and try to remember to look up more info on this. :biggrin:
     
  8. Oct 12, 2016 #7

    davenn

    User Avatar
    Science Advisor
    Gold Member

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: How can the telescopes take photos of distant galaxies?
  1. Galaxy cluster photos (Replies: 2)

Loading...