> https://stsci-opo.org/STScI-01G7ETPF7DVBJAC42JR5N6EQRH.png
Is this for real?! It looks like it came right out of a Sci-Fi movie/book. Could anyone explain how much of this is post-editing magic?
Almost all the light in this image is way off the red end of the human visual spectrum, of course. The shortest wavelength filter is F090W which has a center wavelength of 902nm, about the same color as the light coming out of a TV remote infrared LED, which is barely visible in pure darkness.
This is what it looks like through a film SLR, without the detail enhancing filters: http://www.phys.ttu.edu/~ozprof/3372f.htm Here's a 20 minute exposure through a telescope: http://www.phys.ttu.edu/~ozprof/3372fk.jpg Maybe what you would see with your own eyes through binoculars at a dark site well away from city lights. A dim red smudge, hints of finer detail.
The redshift on the other JWST images is because most of them are of objects that are much, much, much farther away. Infrared telescopes are great for observing those, but that's not the only thing they're used for.
A good way to see this is comparing it to Hubble [1], a lot of the extra detail you see is thanks to IR letting you see the stars behind.
What I was asking is: Is the target's normally-visible light redshifted into the same bands that JWST is measuring, higher? or lower frequency?
That doesn't have anything to do with why JWST uses IR.
NGC3372 is a cloud of (relatively) hot gas and dust. It's emitting broad spectrum blackbody radiation: it's emitting on all wavelengths. You can look at the same cloud at different wavelengths and see different things, telling you what parts of the cloud are at what temperature, or relative chemical composition, or what parts are ionized: http://legacy.spitzer.caltech.edu/uploaded_files/graphics/fu... Nothing here is redshifted, Spitzer is just capturing different light entirely.
In the side by side of JWST and Hubble https://pbs.twimg.com/media/FXecm6vXwAMPhoc?format=jpg&name=... https://pbs.twimg.com/media/FXecnp2XkAE4Rs5?format=jpg&name=... you see broadly the same thing, but Hubble is almost all visible-light while JWST goes deeper into infrared and sees cloud structure that Hubble doesn't.
The NIRCAM instrument on JWST has a wavelength range of about 600 - 5000nm [1]. The human eye is sensitive to around 380nm - 700nm.
To shift blue light (380nm) down to the upper frequency range of NIRCAM (600nm) requires a redshift of:
z = Δλ / λ0 = 0.58
This is related to the velocity of the object by:
z = v / c
and the velocity is related to distance (approximately) by the Hubble constant (H0 ~ 71 km/s / Mpc):
d = v/ H0
So we can rearrange and solve for distance to get:
d = z c / H0 = 8 billion light years.
The southern ring nebula is more like 2000 light years from us, so not even vaguely far enough that NIRCAM would see "originally-visible" light. The deep field image might actually be far enough... the faintest galaxies there might be something like 12 billion light years away [2].
[1] https://www.stsci.edu/jwst/instrumentation [2] https://www.nasa.gov/content/discoveries-hubbles-deep-fields
What causes this "smoke"?
In smokey or smoggy air, the red light is also scattered.
The "smoke" in a nebula is mostly gas and dust. It's either left-over primordeal matter (hydrogen gas, some helium), or ejecta from novas and supernovas --- star-smoke if you will, though it's created by nuclear fusion rather than chemical combustion.
JWST's IR sensors can cut through that dust more readily than Hubble's optical-range sensors could, and pull out more detail on the dust to boot (based on my own viewing of comparative images).
I'm not sure if the dust is reflecting light or glowing from heat, though my hunch is it's mostly reflecting. Stellar gas that gets hot enough will also glow in infrared (or higher) wavelengths, and that might also be picked up by JWST. I suspect there will be targets demonstrating this in future.
Anyway, that looks like science fiction because science fiction borrowed that look from astronomy. https://en.wikipedia.org/wiki/Nebula
how does the scale of color shifting relate to the red-shift present in deep-field subject?
Idly wondering: are the furtherest objects being captured, so red-shifted, that the translation for human viewing done in these images more or less balances that out, so what we see in the translated images for some thickness of distance-bubble, is what we would see from a much closer perspective with the naked eye, akin to "true color." (I.e. so close that the relative red-shift would be insignificant...)
What you'd want to see specifically are the emission spectra showing absorption lines for well-known spectral bands. This shows specifically how red-shifted the light is, and is how red-shift was initially detected.
I doubt that there's an intentional mapping of red-shifted appearance + spectral sensitivity to near-and-unadjusted appearance. Though that might be possible.
In practice, I suspect the bands JWST is receiving don't map well to the RGB sensitivity of the human eye, but insteat JWST's sensitivity is tuned to scientific interests and value.
The coloring is usually done to indicate different temperatures or wavelengths detected, so it can be a bit misleading.
https://images.app.goo.gl/9gqtdbcsBxY6RonY9 https://images.app.goo.gl/pG7sfjLGU9nqmAvH7 https://images.app.goo.gl/JGebDZ7V5EamKoY89
i.e. If we were moving at the same velocity of the Nebula looking with our own eyes.
i.e. What it would look like "in real life if I actually went there"
But that's with a telescope and long exposure & image stacking. But still in RGB as humans would see it.
I guess there would be a point that if you were not so far away, but still far enough away - it would light up the sky. This is emission nebula after all.
BUt if you were in it, it would be so diffuse that you wouldn't know it... perhaps a weird glow if you were near some of the forming stars.
Not much weirder than looking at an X-ray image.