1) as you said, its flux is predominantly in the IR
2) it could have been fainter than the sensitivity of the HST instruments but now seen because of the sensitivity of JWST
But given that it appears so bright in the JWST image similar to other nearby galaxies that do appear in the HST image, your bet on #1 seems reasonable.
Also there is another point: rather than a highly redshifted galaxy it could be a very dusty nearby galaxy (also appearing very red) but if I remember right, that would have a slightly different signature. Dusty galaxies often aren't entirely dusty and have "lanes/channels/streaks" of dust that are interspersed among normal stellar regions, so if it were that, you would be seeing some bright spots outside the infrared. But this one has the shape of a normal galaxy but red all over, suggesting something affects the whole galaxy -- i.e. redshift.
Do the recolored images have any relation to what the original view would have looked like, or is it just arbitrary "artistic license"?
They did not release or talk in much technical detail of how the images were assembled, which I'm sure will be done at some point.
I do not think the colors do correspond (at least not deliberately), for 2 reasons:
First is that the image of the Deep Field ("SMACS") contains galaxies at a range of redshifts. For example there may be galaxies quite near us (redshift z = 0 or close to 0) while others are more distant (the arced galaxies in the image being lensed that this image is famous for, at redshift z = 0.39), where redshift is the measure (1+z) of how much the wavelength light has been multiplied.
So regardless of what color mapping you chose, it would not be a perfect fit for all objects in the field of view. For the galaxies near us in the image (z=0), the wavelengths being converted to RGB don't correspond to what we would see in the optical.
Secondly, if it were remapped especially for the galaxy cluster of interest in this image, I don't think the colors are specifically tuned for that either.
In more detail:
Consider the optical color spectrum we see, ROYGBIV, or let me reverse it in order of increasing wavelength VIBGYOR -- and take the "RGB" 3 colors that might make up an image, or BGR to use that ordering -- this spans a wavelength range of say 400nm, 600nm, 800nm.
The imaging filters available on the NIRCam span 900nm to 4400nm (4.4 micron) and there are 29 of them [0]. Researchers choose which filters to use based on what they wish to study. And recall that the imaging sensor actually outputs grayscale only, it is the filters that give it a color view and individual images in each filter are assembled to create a color composite.
According to an example science program designed to take such images[1], the filters selected to be imaged might be 900nm, 1150nm, 1500nm.
If you applied the redshift of the galaxies (divide by 1.39 from the above info about the cluster of galaxies), the above sampled wavelengths in the image would still correspond to redder parts of the spectrum compared to what is visible if we were seeing the galaxies now: 647, 827, 1079nm.
So, no I don't think the color mapping was chosen to be accurate in a scientific sense of seeing what you would see if the galaxies were brought to the "original" view.
[0] https://jwst-docs.stsci.edu/jwst-near-infrared-camera/nircam...
[1] https://jwst-docs.stsci.edu/jwst-near-infrared-camera/nircam... ("select filters")
However, 2 factors:
1) there is an intrinsic limit I believe to how much more resolution you can recover (maybe a factor of approx. 2x?), for a lot more exposure time needed However, also at these faint levels of brightness you're also competing against intrinsic photon and sensor noise)
2) practically, given the value of the telescope's time and not much more to be gained (science-wise) from achieving this next order of spatial resolution, they want to spend the time on other new targets instead of sitting on the same patch for much more time.
(you can even try this at home: https://petapixel.com/2015/02/21/a-practical-guide-to-creati... )
This kind of mimics the human eye, which is sensitive to those three approximate color frequencies, but it's interesting to note other species besides humans (and, apparently, even some humans)[1] have vision that work with more "filters", or on different spectra (such as honeybees).
I've always found it kind of amazing that so many satellite imaging devices work on far greater spectral ranges with far more color filters, being able to discern far more information than we could with the naked eye (but in essentially the same way).
Will there be thousands of additional extremely red shifted galaxies?
There would be negligible space without a light emitter.
> Will there be thousands of additional extremely red shifted galaxies?
Yes, and also those that were too faint, but not necessarily extremely red-shifted.
I don't have the info at hand -- do you know what was the resolution of HST optical/NIR imagers versus JWST new imagers?
Not a new thing.
Herschel space observatory operated in same location (L2-point) as JWST and it was IR telescope. https://www.google.com/search?q=Herschel+space+observatory+i...
Mirror sizes:
Hubble 4.0 m2 (43 sq ft)
Herschel 9.6 m2 (103 sq ft)
JWST 25.4 m2 (273 sq ft)
Herschel, while impressive also, was far-IR (if I recall) and much lower resolution, which was good for certain research areas, but less complementary to the HST deep fields for the, well, currently fashionable, recent study of galaxies at high redshift.
HST is already imaging at diffraction-limited resolution (with proper post-processing). It would need a bigger mirror to get there.
> stunning images was enough to get the public to support a $10B project.
I don't believe public support is relevant; is there public support for the >$700B a year spent on the military?
Everyone in “big science” remembers the cautionary tale of the Superconducting Super Collider, which was cancelled mid-project when it became politically viable to oppose it as a waste of money. The circular tunnel is still sitting dusty and abandoned down in Texas while CERN runs another round on the LHC.
Big results that gather public praise go a long way toward making sure the next big science project will at least be seriously considered.
Global force projection at the benefit for all Western economies is very expensive. This money is required to even allow the form of economy "the West" is running.
How else were you going to keep up the Pax Americana that enables globalization by making significant global trade networks even possible in the first place? Who's gonna insure your freighter if international waters aren't protected by Western navies? Pirates, rogue states closing important channels, at will seizures for no reason... the list is long.
As the Pax Americana will likely soon fade through growing influence of the BRICS nations and "America First"-style ideologies, the 700B will probably wither away quite fast in the next decades - along with all the benefits we enjoyed since WW2.
Just one illustration. How man South American or African nations support the sanctions against Russia? How many Asian nations that are not Japan?
Of course. It's tempting to think we're in this new lovey-dovey age of an improved/superior humanity, but the reality is man's baser instincts are kept in check by BFGs and MAD.
1) The galaxy is moving away from us. This is most like the classic Doppler effect, but because of the high relative velocities involved, time dilation needs to be taken into account to model the red shift accurately, thus at least special relativity should be used.
2) The light travels through space with different curvature. For example, light originating near a very massive star will red shift when moving away from that star because it moves into less curved space. General relativity is needed to explain this effect.
3) The light travels through expanding space. For very distant galaxies this becomes the dominating factor of red shift, as we see an amount of red shift directly corresponding to their distance from earth. General relativity also explains this effect.
Your comment is way, way over the top. Their observation is entirely correct, maybe not in your circles, but certainly it's what I'm also seeing on Facebook and twitter.
Hell, NASA posted "The razor-sharp resolution of the @NASAWebb imagery was enough to bring astrophysicist Jane Rigby to tears."
Certainly people here and discussing it among those who get to watch these announcements during their day, are a more knowledgeable and appreciative group of the details. They have the time and info to know the "new" aspect.
I was just making the point that in the most headline-grabbing and CNN/newspaper science-writer genre, probably their and their audience just sees the image sharpness as they flip through the news.
Pot, meet kettle. Except you are flat out an arse while GP was mostly innocent in their action I feel.
The thing that I don't like about the new images is the abuse of star flare effect. The colors are okay, but the flares... that's simply too much.
While this is very important for scientific work (easier to see planets!) it is less appealing to the eye. Also note that some JWT images have some faint blue streaks which in effect are diffraction spikes from bright stars outside the field of view.
People seem most impressed by the apparent increase in resolution of the images, which is not from a certain point of view the hardest thing to do . HST might have done that if its instruments had been of different pixel size or imaging array size / focal length. Ok, the much larger mirror is an achievement. But anyway, the resolution of the images is often not what really is the limiting factor for photometric observations. Yes it is sharper/higher resolution, but that wasn't the key selling point.
The new thing is observations in the IR, which is somewhat a technical footnote in many gushing announcements of these images (or some discussion here too). And the general public knows little about that detail's importance, especially since the images are stylized / colored anyway to look just like RGB images that we are so familiar with. But everyone can easily appreciate a sharper image.
Anyway, still a momentous achievement. And thank god we have a scientific field where stunning images was enough to get the public to support a $10B project.
**
Edit to add: I did not mean to detract from or diminish anyone's appreciation of the images and accomplishment at whatever level they are enjoyed. And of course many here are technically knowledgeable about the IR aspect. I just write to point out that for the most headline-grabbing images and newspaper writers, the sharpness of the images over the actual IR frontier is what grabs the attention.