How do we see distant galaxies?


by Yosty22
Tags: distant, galaxies
Yosty22
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#1
Jul30-13, 04:56 PM
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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?
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phinds
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Jul30-13, 05:31 PM
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Quote Quote by Yosty22 View Post
I understand that the Hubble Space Telescope is able to see these distant galaxies we discover, but how exactly does Hubble do that?
I'm not clear on why you think it is a problem.

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.
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.

That is like we cannot see outside of our galaxy, because the light from our own galaxy is not allowing us to do that.
Again, you have been misinformed.

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?
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.
Dotini
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Jul30-13, 05:48 PM
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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_discove...-ison-in-space

Drakkith
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Jul30-13, 11:52 PM
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How do we see distant galaxies?


Quote Quote by Yosty22 View Post
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?
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.
davenn
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Jul31-13, 07:48 PM
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Quote Quote by Drakkith View Post
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.
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
russ_watters
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Jul31-13, 08:09 PM
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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.
Drakkith
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Jul31-13, 08:38 PM
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Quote Quote by russ_watters View Post
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.
Quit one upping everyone or I'm sicking Phinds on you!
phinds
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Jul31-13, 09:19 PM
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Quote Quote by drakkith View Post
quit one upping everyone or i'm sicking phinds on you!
arf !
davenn
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Jul31-13, 10:38 PM
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hopefully the OP got the understanding
unfortunately he/she never responded :(

Dave
Damo ET
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Aug1-13, 08:28 PM
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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.


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davenn
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Aug1-13, 09:01 PM
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hi there Damo

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

Dave
Damo ET
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Aug2-13, 02:36 AM
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True, and it doesn't take much effort in forum etiquete to achieve this either.


Damo
phinds
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Aug2-13, 08:06 AM
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Quote Quote by Damo ET View Post
True, and it doesn't take much effort in forum etiquete to achieve this either.


Damo
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.
travboat
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Aug6-13, 04:39 PM
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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.
phinds
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Aug6-13, 04:50 PM
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Quote Quote by travboat View Post
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.
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.
Drakkith
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Aug6-13, 07:10 PM
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Quote Quote by phinds View Post
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.
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.
phinds
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Aug6-13, 07:55 PM
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Quote Quote by Drakkith View Post
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.
Glad to see you are supporting the point I was making here:

http://www.physicsforums.com/showthread.php?t=704511
Drakkith
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Aug6-13, 08:00 PM
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Quote Quote by phinds View Post
Glad to see you are supporting the point I was making here:

http://www.physicsforums.com/showthread.php?t=704511
That's fair.


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