What does space look like from space?


by CGameProgrammer
Tags: space
CGameProgrammer
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#1
Feb28-04, 09:01 PM
P: 6
This is a pretty simple question, but it's often portrayed in art as basically being how it looks when you're zoomed in really far, which it obviously is not. Is it reasonable to assume that from any typical point within a galaxy, looking at the galaxy with a human-eye field of view, that all stars are tiny dots and interstellar gases are either too thin to see or they appear very faded, like how we see our Milky Way (thin band of light)? I hope you can decipher that run-on sentence. Are nebulae thicker than galaxtic dust, and thus more visible to the naked eye, even from up close?
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cookiemonster
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#2
Feb28-04, 09:37 PM
P: 991
I think the answer to your question is along the lines of "Depends where you're looking from." It's possible (theoretically, obviously not practically just yet) to move to a point such that the view we see from telescopes are "full-sized." But it's worth noting that most pictures of star stuff are colored, that is, that's not what they'd look like to the naked eye.

cookiemonster
CGameProgrammer
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#3
Feb28-04, 11:02 PM
P: 6
Originally posted by cookiemonster
I think the answer to your question is along the lines of "Depends where you're looking from." It's possible (theoretically, obviously not practically just yet) to move to a point such that the view we see from telescopes are "full-sized."
Really? How? I mean, you can look at a telescope image and seen 12 large stars, but each of those stars could be 10 light-years apart, so from any one of them, all the others would be dots.

And yeah, I'm aware of false coloring, but a number of the images are supposed to be true-color, aren't they? Although of course that's still different from how things look up-close, like telescope images of planets versus pictures taken from probes flying by.

cookiemonster
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#4
Feb29-04, 12:07 AM
P: 991

What does space look like from space?


I don't think you're ever going to fit 12 large stars that are each 10 LY apart into a single frame, with or without a telescope.

Now that I think about it, the perception of the stars would change. But I imagine that you'd still be more than far enough away that it wouldn't make much of a difference.

Probes probably take true-color images of nearby planets and stuff (some pretty pictures of Jupiter out there). But most pictures of far-away objects are re-colored, as far as I know. Maybe somebody else can offer a bit more insight.

cookiemonser
CGameProgrammer
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#5
Feb29-04, 12:35 AM
P: 6
I meant they can be 10LY apart along the viewing axis. Example: You're standing at the end of a long perfectly straight road. If you look far down it with a telescope, zoomed in very far, all the cars will appear to be the same size even if each car is actually spaced a mile apart, since perspective matters less as your field of view narrows.

And I know that, usually, the probes take true-color images, but I just meant a true-color image taken near the planet will look different than a true-color image taken from a telescope from far away. I don't know the reason but that seems to be the case.
cookiemonster
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#6
Feb29-04, 12:46 AM
P: 991
Originally posted by CGameProgrammer
If you look far down it with a telescope, zoomed in very far, all the cars will appear to be the same size even if each car is actually spaced a mile apart, since perspective matters less as your field of view narrows.
This is simply not true. Objects farther away always look smaller.

Originally posted by CGameProgrammer
And I know that, usually, the probes take true-color images, but I just meant a true-color image taken near the planet will look different than a true-color image taken from a telescope from far away. I don't know the reason but that seems to be the case.
Probably a number of causes of this, ranging from Doppler shift to atmospheric interference.

cookiemonster
Nereid
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#7
Mar3-04, 09:24 PM
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You have to be pretty close to a star for it to have a visible disk (i.e. not look like a point); for 'average' stars, if you're further away from one than Pluto is from the Sun, you will see just a point (there are exceptions of course). Even in the heart of the densest star cluster in the Milky Way, all stars will look like points.

Colour perception is a very complex subject, and answering questions on what colour gaseous nebulae would appear to be from various vantage points is quite tricky. Suffice it to say that you can be close enough to some nebulae as to be able to see they're coloured ... but paradoxically, if you're in most nebulae, you won't notice it!

Does the Earth's atmosphere change the colour of a celestial object? Yes, but not noticably if you're looking pretty much straight up (near the horizon it's a totally different story).

Can you see the colours of nebulae with your eye, through a telescope? Yes; the bigger the telescope (light-gathering capability, basically the size of the primary mirror), the brighter the nebulae (caveats apply), and big enough, the colours will be clear.
CGameProgrammer
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#8
Mar3-04, 09:57 PM
P: 6
Originally posted by Nereid
You have to be pretty close to a star for it to have a visible disk (i.e. not look like a point); for 'average' stars, if you're further away from one than Pluto is from the Sun, you will see just a point (there are exceptions of course). Even in the heart of the densest star cluster in the Milky Way, all stars will look like points.

Colour perception is a very complex subject, and answering questions on what colour gaseous nebulae would appear to be from various vantage points is quite tricky. Suffice it to say that you can be close enough to some nebulae as to be able to see they're coloured ... but paradoxically, if you're in most nebulae, you won't notice it!

Does the Earth's atmosphere change the colour of a celestial object? Yes, but not noticably if you're looking pretty much straight up (near the horizon it's a totally different story).

Can you see the colours of nebulae with your eye, through a telescope? Yes; the bigger the telescope (light-gathering capability, basically the size of the primary mirror), the brighter the nebulae (caveats apply), and big enough, the colours will be clear.
Thanks for the reply, Nereid -- much appreciated. The star density in the denser parts of the galaxy was something I was wondering about, but you say they'd all look like points. Makes sense, since the sun is merely a bright star from Pluto.

A google search about the star density in the galactic center revealed this page which says the stars are 1000 AU apart, and elsewhere I found Pluto is 40 AU from the sun. So the stars are dots, but the link says the sky would still be very bright... I guess because they're so close together?


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