How do we see distant galaxies?

  1. I understand that the Hubble Space Telescope is able to see these distant galaxies we discover, but how exactly does Hubble do that? I have heard the analogy that our galaxy and our place in it is like being in the middle of a forest. If we look any direction, we cannot see outside the forest because we are blocked by the very same forest. That is like we cannot see outside of our galaxy, because the light from our own galaxy is not allowing us to do that. Since the Hubble Space Telescope can see in forms of light outside the visible spectrum, is this why it is able to see "through" our galaxy to discover more distant and older ones?
     
  2. jcsd
  3. phinds

    phinds 9,148
    Gold Member

    I'm not clear on why you think it is a problem.

    Totally wrong analogy. We DO have trouble seeing THROUGH the Milky Way, but that's mostly in one direction (we're off to the edge). There is at least one galaxy that you can see with the naked eye, and more that you can see with amateur telescopes and the Hubble is WAY beyond being an amateur telescope.

    Again, you have been misinformed.

    That's how some telescopes do it but the Hubble does amazing things with just visible light. Google "Hubble Deep Field" for example.

    Also, the Hubble is hardly the only telescope that studies far-off galaxies in the visible spectrum.
     
  4. Dotini

    Dotini 759
    Gold Member

    Unfortunately, the term "smudge" is often associated with viewing distant galaxies.
    Below is a Hubble shot of Ison with the caption including, "In general, redder things are older, more evolved, than blue things – this is true both for the crosshair-spiked stars and the smudges of distant galaxies."
    http://hubblesite.org/hubble_discoveries/comet_ison/blogs/blog-exclusive-ison-in-space
     
  5. Drakkith

    Staff: Mentor

    Not really. To use your forest analogy, imagine the forest is on a totally flat plain and is very very sparse, but very very big. Looking UP you can easily see through the canopy because the trees are very very far apart. But, the closer your start to look towards the horizon, the more the trees block your view until eventually you cannot see through the forest.
     
  6. davenn

    davenn 3,883
    Science Advisor
    Gold Member
    2014 Award

    and to take that analogy a little further .... we are at the edge of the forest so looking in directions away from the centre of the forest ( Milky Way) we have an unobstructed view of most of the universe


    Dave
     
  7. russ_watters

    Staff: Mentor

    Try this one instead:

    We're at the end of a long, straight highway lined with telephone poles. In any direction we look other than the one directly down the line of telephone poles, our vision is not obstructed. I believe this analogy is actually closer to the reality of the relative densities and angle of view obstruction.
     
  8. Drakkith

    Staff: Mentor

    Quit one upping everyone or I'm sicking Phinds on you!
     
  9. phinds

    phinds 9,148
    Gold Member

    arf !
     
  10. davenn

    davenn 3,883
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    2014 Award

    hopefully the OP got the understanding
    unfortunately he/she never responded :(

    Dave
     
  11. The good thing is that he doesn't need to. The multitude reading the post have also potentially learned something new whether the OP comes back or not. Stuff like this arms me with analogies to use when I too need to try and explain why some things are the way they are to the muggles in my life. Thanks guys.:smile:


    Damo
     
  12. davenn

    davenn 3,883
    Science Advisor
    Gold Member
    2014 Award

    hi there Damo

    no they don't, but its always nice when some one does to say "thanks for clearing that up" etc :)

    Dave
     
  13. True, and it doesn't take much effort in forum etiquete to achieve this either.


    Damo
     
  14. phinds

    phinds 9,148
    Gold Member

    Yes, but it isn't really a matter of "form etiquette" so much as it is just a matter of simple every-day politeness, which some people don't have. You'll see that here from time to time. People just not answering questions that they are speciifically asked, or posting and then never responding.
     
  15. Well, I learned something from this thread, so thanks to the contributors. Now, it's my turn to nit-pick, because both of you are correct (Damo & phinds) ;)

    When I type "define etiquette" into google, I get this.

    et·i·quette
    /ˈetikit/
    Noun
    The customary code of polite behavior in society or among members of a particular profession or group.
     
  16. phinds

    phinds 9,148
    Gold Member

    Glad you learned something, and it's OK to point out that Damo is right, but PLEASE don't tell Drakkith he's right. It goes to his head and he gloats.
     
  17. Drakkith

    Staff: Mentor

    What's that I hear, Phinds? The snip snip of scissors at the vet?

    I don't think we need a telescope to see where this is going. :tongue:
     
  18. phinds

    phinds 9,148
    Gold Member

  19. Drakkith

    Staff: Mentor

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