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.
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.
Many in that set are accurate colours ......
many have been severely enhanced and no longer look like reality
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
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.
Cor! I wish my telescope was as good as yours.
davenn cheats ... he knows stuff.
but I tell you something .... It doesn't take being on PF for very long to realise there are a lot of people that know a lot more stuff !
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
Don't worry. I hear people going into geology usually have a 'rocky' start.
Followed by in depth study?
Well, of course, since they are striving for cavernous knowledge
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