Why do galaxy and galaxy clusters look so colorful?

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Discussion Overview

The discussion revolves around the colorful appearance of galaxies and galaxy clusters, exploring the reasons behind these colors as seen in images, including considerations of photography techniques and the physics involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question the authenticity of colors in internet photos, suggesting that many images are color-enhanced and may not represent true colors.
  • Others argue that while some images are accurate representations, many have been significantly altered or are artistic impressions rather than actual astrophotography.
  • A participant notes that the colors observed can be attributed to the composition of gases in nebulae and the temperature of the stars illuminating them.
  • There is mention of imaging techniques, with some participants explaining that galaxies are typically imaged using broadband filters, while nebulas often require narrowband filters, leading to different color representations.
  • One participant describes the "Hubble palette" used in processing narrowband images, assigning specific colors to different wavelengths to create full-color pictures.

Areas of Agreement / Disagreement

Participants express differing views on the authenticity and representation of colors in astrophotography, with no consensus reached on the extent to which images are enhanced or accurately depict reality.

Contextual Notes

There are limitations regarding the definitions of "true color" and the effects of various imaging techniques, which remain unresolved in the discussion.

Riotto
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Why do galaxy and galaxy clusters look so colorful?
 
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Riotto said:
Why do galaxy and galaxy clusters look so colorful?
And what makes you think they are? Internet photos? Most of those are color enhanced with a combination of overlays from varying frequency ranges shifted to the visible.
 
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phinds said:
And what makes you think they are? Internet photos?.

Yes. Are the colours in these pictures completely unreal? I thought there must be some 'atomic physics and spectroscopy theory' behind these beautiful pictures.
 
We've had several posts here on PF on exactly this issue. As I recall, there are more true color pics out there than I had expeced but I have no idea how to tell which is which. I suggest a forum search.
 
A lot of the photography has to be adjusted to make a meaningful image to a human.
X ray images and radio images are not comprehensible to us without that, other than just as numerical data.
 
Riotto said:
Yes. Are the colours in these pictures completely unreal? I thought there must be some 'atomic physics and spectroscopy theory' behind these beautiful pictures.

Many in that set are accurate colours ...

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06be2886d972b643faa6b54ae196d273.jpg


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many have been severely enhanced and no longer look like reality

2ef6f797d38c9f8e2afef17753304a60--phone-wallpapers-space-iphone-wallpaper.jpg


7ed86a288e4940a29d21981c7d664f68.jpg


74481d2c7ea93431887797e2fe7e42bb--galaxy-universe-the-universe.jpg
and there are also a number of pure artist's impressions there too ... that is, not actual astro images

There is a lot of colour out there with the variety in composition of the gasses in the nebula
the colour/temperature of the star illuminating that gas

Dave
 
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I would say that most pictures of galaxies and galaxy clusters are decent approximations of what they would look like if your eye could gather enough light to make them bright enough to see the colors. We don't usually image galaxies with narrowband filters, but with broadband filters, producing images similar to what a normal DSLR camera creates. Still, many of these pictures have had their colors enhanced, so the color contrast wouldn't be as high as you usually see in pictures.

Pictures of nebulas are far more likely to be false color. This is because nebulas often emit light predominantly in a handful of specific wavelengths instead of over a broad spectrum like stars (and galaxies) do. A popular set of narrowband filters used to image nebulas consists of Hydrogen-Alpha (HA), Oxygen-3 (OIII), and Sulfur-2 (SII) filters. HA and SII both pass light in the red part of the visible spectrum, while OIII passes light in the blue-green part. During processing, we often assign these narrowband images a different color than that which they imaged. The so called "Hubble palette" makes SII = red, HA = green, and OIII = blue to produce full color pictures.
 
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davenn said:
Many in that set are accurate colours ...

View attachment 206019

View attachment 206020

View attachment 206021many have been severely enhanced and no longer look like reality

View attachment 206022

View attachment 206023

View attachment 206024and there are also a number of pure artist's impressions there too ... that is, not actual astro images

There is a lot of colour out there with the variety in composition of the gasses in the nebula
the colour/temperature of the star illuminating that gas

Dave
Cor! I wish my telescope was as good as yours. :-p
 
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sophiecentaur said:
Cor! I wish my telescope as as good as yours. :-p
davenn cheats ... he knows stuff.
 
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  • #10
phinds said:
davenn cheats ... he knows stuff.

hahaha :biggrin:

but I tell you something ... It doesn't take being on PF for very long to realize there are a lot of people that know a lot more stuff ! :smile:
 
  • #11
davenn said:
hahaha :biggrin:

but I tell you something ... It doesn't take being on PF for very long to realize there are a lot of people that know a lot more stuff ! :smile:
All those clever clogs who actually KNOW Maths! V humbling.
 
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  • #12
sophiecentaur said:
All those clever clogs who actually KNOW Maths! V humbling.

Uh huh ... maths and I do not have a good relationship ...
not being able to do the required two first year maths papers at uni is what stopped me finishing my BSc in geology :frown:
 
  • #13
davenn said:
Uh huh ... maths and I do not have a good relationship ...
not being able to do the required two first year maths papers at uni is what stopped me finishing my BSc in geology :frown:

Don't worry. I hear people going into geology usually have a 'rocky' start.
 
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  • #14
Drakkith said:
Don't worry. I hear people going into geology usually have a 'rocky' start.
Followed by in depth study?

DON"T START!
 
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  • #15
sophiecentaur said:
Followed by in depth study?
Well, of course, since they are striving for cavernous knowledge
 
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