Compare Webb's Images to Hubble
johnedchristensen.github.io
johnedchristensen.github.io
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.
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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.
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")
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).
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... )
I don't have the info at hand -- do you know what was the resolution of HST optical/NIR imagers versus JWST new imagers?
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.
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.
> 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?
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?
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.
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.
HST is already imaging at diffraction-limited resolution (with proper post-processing). It would need a bigger mirror to get there.
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.
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.
More comparisons on Twitter, some zoomed in:
- https://twitter.com/Batsuto_/status/1546899241880240128
- https://twitter.com/Batsuto_/status/1546900387931766784
- https://twitter.com/JBWillcox/status/1546881033597075457
- https://twitter.com/jason4short/status/1546626672488632321
I'm not a physicist, so I've only recently learned about redshift. Hubble's deep field images were very dark red/orange because further objects appear redder (into infrared) before they disappear to the observer. Webb's sensors are more red/infrared-sensitive than Hubble's, so along with extremely fine, super-cooled optics using exotic materials to align and capture every single photon, its red sensitivity allows Webb to peer deeper, further, and dimmer than we've ever been able to before.
And I've read that the "spikes" coming off the brighter stars are generally from stars in our own galaxy and they're not lens flares. They're caused by the edges of the telescope. Hubble's stars would have 4 spikes in a cross; Webb has 6 in a snowflake because of the shape of Webb's mirrors having 6 sides. Or something like that.
>This happens through light scattered by the imaging mechanism itself, for example through internal reflection and forward scatter from material imperfections in the lens. Lenses with large numbers of elements such as zooms tend to have more lens flare, as they contain a relatively large number of interfaces at which internal scattering may occur.
The spikes from JWST are primarily caused by the edges of the mirrors and the three support struts.
There likely is some amount of lens flare (though I don't know if it is significant, the optics are Very Good), but the dominant artefact is the diffraction spikes.
That sounds to me like "light scattered by the imaging mechanism".
https://en.wikipedia.org/wiki/Photographic_filter#Cross_scre...
https://en.wikipedia.org/wiki/Diffraction_spike
EDIT: It may be caused by both the diffraction spikes from the supports struts and the shape of the mirror and aperture. I'm not really sure. The JWST images also seem to have two additional small spikes that look more like the diffraction pattern from a single strut, which could also be a support strut for a stop further down the optics chain.
Hank Green on TikTok did a neat, quick demonstration in video form.
Thanks!
https://blogs.nasa.gov/webb/2022/02/03/photons-incoming-webb...
If someone got starnet to remove the stars in the JWT images it wouldn't then be hard to go overlay stars back in without the diffraction.
I'm trying to understand how much the improvement is "speed of convergence" vs. "quality of asymptotic result". (Though... is that even a valid way of trying to understand things?)
When you do long exposure, any kind of movement, even very small, can degrade your image.
How JWST handles movement during long exposure is a good question. Same with hubble.
I really hope you were trolling with this response
The most pronounced effects might be paralax of nearby stars to thousands of light-years at the outside. That would be observable in images taken at opposite sides of Earth's orbit around the Sun, a baseline of about 300 million km (186 million miles). Even that will be phenomenally small, too small to be observable for most objects within our own galaxy (the Milky Way) let alone the distant objects JWST is most concerned with.
From Wikipedia:
In 1989 the satellite Hipparcos was launched primarily for obtaining parallaxes and proper motions of nearby stars, increasing the number of stellar parallaxes measured to milliarcsecond accuracy a thousandfold. Even so, Hipparcos is only able to measure parallax angles for stars up to about 1,600 light-years away, a little more than one percent of the diameter of the Milky Way Galaxy.
The Hubble telescope WFC3 now has a precision of 20 to 40 microarcseconds, enabling reliable distance measurements up to 3,066 parsecs (10,000 ly) for a small number of stars.[10] This gives more accuracy to the cosmic distance ladder and improves the knowledge of distances in the Universe, based on the dimensions of the Earth's orbit.
https://en.wikipedia.org/wiki/Stellar_parallax
JWST's optical acuity is roughly similar to Hubble --- despite the larger mirror surface, it's using longer wavelengths of electromagnetic radiation, with lower resolving power.
Movement of the JWST itself is kept to an absolute minimum for obvious reasons. It would simply be unusable as a telescope if this weren't the case.
Absolute motion of objects being imaged ... also isn't a factor, as the maximum resoultion of JWST (the smallest pixels on an image) are still tremendous. It's possible that a nearbye (neighbouring galaxy) nova event might generate observable motion over days or weeks, but even that is unlikely. The interesting stuff in that event is actually the changes in brightness and evolution of light emissions, for the most part.
In the case of the Carina Nebula image 8,500 light years distant (that is, astronomically near), the individual dust segments are light years in length. The distance from the Earth to the Sun is roughly 1/64,000th that distance --- too small to visualise in thos images. The individual stars show are not dots or disks, but points, whose apparent size is a matter of refraction and saturation effects on the JWST itself.
Even where there migh be any movement, individual images are composed of multiple exposures and "stacked" to take median observed signal strengths. This is, in a way, to eliminate motion effects, but the moving entities are cosmic rays which create random signatures on the sensors of JWST, and not movement of the telescope or its targets themselves.
To the "can Hubble do anything Webb can do but with more time", the answer is no, due to the lack of mid-infrared sensitivity, among other things like atmosphere.
A major issue with Hubble & JWST comparisons is just that they're designed to look at different wavelengths of light. A lot of what JWST will see is completely invisible to Hubble, and no amount of observing time can compensate for that.
>could Hubble achieve the same quality of images as Webb if it was given 100x (or whatever) more time exposure?
No, for a different and simpler reason: Hubble isn't as sensitive in the infrared as Webb. A lot of the stars and structure Webb has revealed in the two nebulae especially is due to it picking up a lot more of the infrared light to which the gas and dust of the nebulae are essentially transparent. In other words the data is qualitatively different in addition to the increased resolution. This also will see much older light which is redshifted(the longer the travel, the greater the shift) out of Hubble's range of sensitivity.
As for the quantitative part, I guess mirror size is what you'd want to look at? Hubble has a single circular primary mirror with a diameter of 2.4 metres.[0]
Webb has 18 hexagonal mirror segments that are combined into the equivalent of a circular mirror with diameter 6.5m. That is ~6.25 times the light collection area of Hubble(25.4m² vs 4m²)[1]
0: https://en.wikipedia.org/wiki/Hubble_Space_Telescope
1: https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Fea...
This would have to be scaled by the wavelength being observed, for a resolution comparison. Hubble actually has better absolute resolution, when viewing shorter the wavelengths that JWT can't sense (0.05 arcseconds vs JWT 0.1 arcseconds).
Then, in some sense, the first part of my explanation is most of the story in the case of comparing MIRI(mid-infrared instrument) to hubble in the near-infrared.
But in comparing NIRCAM to Hubble in the near-infraread JWST would in fact have greater resolution, no?
It's a matter of speed not distance, isn't it?
However, it also seems like due to galaxies further away having a larger expansion speed, typically they are more redshifted.
So farther away means faster relative speed and thus more redshifted (Doppler effect) Farther away also means older light (due to the finite speed of light).
Putting that all together means that to observe old light from the start of the universe we have to look in the IR spectrum.
The short version - it converges faster (probably like 5-10x faster), but also (as everyone else said) works in different wavelengths.
You can think of a telescope as a "photon bucket." The number of photons it collects is proportional to the area of the aperture. Webb's aperture area is 25.4 square meters, while Hubble's is 4 square meters, so roughly speaking JWST will get photons about 6 times quicker than Hubble.
But that's only the roughest measure. Once you've got the photons, what do you do with them? You send them to a detector. There's loss in this process - you bounce off of mirrors, with some small loss. You pass through band filters to isolate particular colors, which have more loss. The detector itself has an efficiency; in CCD cameras people speak of "quantum efficiency" - the probability that a photon induces a charge that can be counted when you read out the chip. That quantum efficiency depends on the photon's wavelength.
Furthermore - the longer your exposure, the more cosmic rays you get which corrupt pixels. You can flush the CCD more often and detect the cosmic rays and eliminate them, but you'll eventually brush against the CCD's read-out noise, which is a "tax" of noise you get every time you read out data.
So this all get's complicated! People spend many years characterizing detection capabilities of these instruments, and write many pages on them.
JWST's capabilities are described here: https://jwst-docs.stsci.edu/jwst-near-infrared-camera/nircam...
HST's camera is more complicated to characterize, partly because it's older. Radiation has damaged and degraded many of the components so they have a lot of noise. The details of how this works are at the edge of human knowledge, so we don't have a great model for them. From the STIS handbook:
Radiation damage at the altitude of the HST orbit causes the charge transfer efficiency (CTE) of the STIS CCD to degrade with time. The effect of imperfect CTE is the loss of signal when charge is transferred through the CCD chip during the readout process. As the nominal read-out amplifier (Amp D) is situated at the top right corner of the STIS CCD, the CTE problem has two possible observational consequences: (1) making objects at lower row numbers (more pixel-to-pixel charge transfers) appear fainter than they would if they were at high row numbers (since this loss is suffered along the parallel clocking direction, it is referred to as parallel CTE loss); and (2) making objects on the left side of the chip appear fainter than on the right side (referred to as serial CTE loss). In the case of the STIS CCD, the serial CTE loss has been found to be negligible for practical purposes. Hence we will only address parallel CTE loss for the STIS CCD in this Handbook.
The current lack of a comprehensive theoretical understanding of CTE effects introduces an uncertainty for STIS photometry.
Hubble has a high-res camera, and a separate wide-angle camera. Hubble's high-res camera actually outperforms JWST - it can resolve down to 0.04 arcsec, while JWST's can go to around 0.1 arcsec. But JWST's camera has a much wider field of view.
Now both have resolutions and stuff. But no matter how big the resolution or how long it stares, cam1 is fundamentally blocked by the wall. It can take extremely high res photos of things inside the wall, but it can never see anything behind the wall.
Cam2 could have infinitely higher quality than cam1 — because who knows, there can be 100, 1000, million or a never ending world of things behind that wall that can never be seen or captured by cam1.
Cam1 is Hubble, cam2 is JWST, and the wall is infrared wavelength which is all around us. JWST can peer deeper into the _same area_ of space, and see more things behind the infrared wall, which Hubble can never see.
What am I missing?
What JWST can do is show new things that have never been seen before, but obviously it's a bit hard to schedule that sort of photos.
Getting readings from the atmospheres of exoplanets will give us an idea of what population and percentages could harbor life. We may even get a whiff of some tell tale signs of industry, and that would change life on earth forever.
1. Scientific American comparing how far back in time Webb can see vs Hubble: https://youtu.be/nBDHqquK_8k&t=2m8s
2. NASA scientist reviewing Webb’s Carina Nebula image, explaining what Webb is unveiling for the first time, and comparing to the same image from Hubble: https://youtu.be/3y6iWi95ypc&t=2m17s
3. Good overview of Webb and its differences from Hubble: https://youtu.be/JzDWpvtDJ9g
It's got a much bigger mirror, so why is this the case? Well, it's because the Webb works primarily in the longer, infrared part of the spectrum, not the visible. Resolution is related to the diameter of the mirror and the wavelength being studied - the longer the wavelength, the bigger the mirror you need to achieve the same sharpness.
But working in the infrared part of the spectrum means that Webb can look further back into the past, because the oldest light created by the earliest galaxies has redshifted out of the visible spectrum because of the expansion of the universe. So we'll be able to collect and see much older light from much younger galaxies with Webb that Hubble literally cannot detect because of this redshift.
On top of this, infrared, being a longer wavelength than visible light, allows us to see through dust clouds more readily. Notice how many more stars are visible in the Carina Nebula comparison.
Lastly, the Webb has other instruments such as a spectrograph that allows us to determine the chemical composition of distant objects (such as planets). We can point it at an exoplanet and determine, say, if it has water in its atmosphere.
In total, it means marginally better photos for the general public, but a great deal of new data for scientists that should greatly further our understanding of the universe.
With that said, NASA is not unaware of the PR value of pretty pictures (they weren’t the point of Hubble either!) and I have no doubt that we will be getting plenty of them.
To explain that concretely: Hubble was launched in 1990 and was fully functional once got its eyeglasses in 1993. But it wasn't until April 1995 that Jeff Hester was studying photo evaporation in the eagle nebula and motivated by studying the concentration of different molecular gasses, created a color image by mapping the narrow SII, Halpha, and OIII molecular lines filters to RGB (a false color image, called SHO or the 'Hubble pallet' by astrophotographers)-- creating the iconic "Pillars of Creation" image https://en.wikipedia.org/wiki/Pillars_of_Creation#/media/Fil... .
Hubble's large aperture and freedom from atmospheric distortion and light polution obviously contribute greatly to the image-- but much of the purely aesthetic beauty of the image, beyond the target, comes from the process and processing choices as illustrated by the many lovely images of the same object created by amateur astronomers whos processing follows in Dr. Hester's footsteps. E.g. https://www.astrobin.com/lglsd8/ https://www.astrobin.com/i1wffo Today, SHO images of many targets are produced by advanced amateurs with relatively inexpensive equipment, resulting in many breathtaking images of a sort that never existed before these techniques were popularized by the Hubble telescope. (random example: https://www.astrobin.com/fzp6u2 )
By the same token the JWT likely has locked inside it a tremendous potential for images which are both intellectually and aesthetically pleasing waiting to be unlocked through the skill and practice of people working with the data and their discovery of targets best matched to the instrument and those processing techniques.
Targets which are likely to be particularly aesthetically stimulating (as opposed to only intellectually stimulating) are also only a portion of what gets studied. A differential spectral measurement showing an oxygen atmosphere won't be much to look at-- but it will have a tremendous intellectual beauty.
Maybe in the future we'll see one of the billionaire space spacefarers partner up with some amateur astrophotographers to launch some modest equipment optimized for making aesthetic images (e.g. using optical designs that are free of diffraction spikes, like refractors or SCT reflectors). Who knows-- they might also make some interesting scientific discoveries because it's hard to study the aesthetic beauty of the universe without finding intellectual beauty of vice versa.
It might also be that processing techniques from JWT NIRcam images help terrestrial astrophotographers make better images. There are some reasonably large windows of NIR spectrum that we can image from earth-- e.g. J-band from 1170nm to 1330nm has good atmospheric transmission. And there is a lot in favor for terrestrial imaging in J-band: Light pollution is much less there, wavefront distortion from seeing is reduced, scattering (which follows the inverse 4th power of wavelength) is vastly lower. As a result you can even image the stars in the daytime with J-band. The big barrier is sensors because silicon sensors are blind past about 1100nm. The sensors used by JWT's NIRcam cost about $350k each and have to run at cryogenic temperatures. But sensor technology is improving (e.g. https://www.qhyccd.com/qhy990_qhy991/ QHY990 is more like $24k), and JWT might help drive along development by finding targets and processing techniques that could also be applied on earth just as happened with hubble SHO.
Based on my understanding of astronomy, the real research starts when scientists zoomed way in, thus the "enterprise upgrade" (increased resolution I assume?) is exactly what they're looking for.
Those published pictures are probably just for show (/to proof that the taxes you paid is have been used on a real project).
The actual science is yet to come, but will likely not look as spectacular to the layperson.
Edit: Here is an overview of the science that JWST is going to be doing in Cycle 1: https://www.stsci.edu/jwst/science-execution/approved-progra....
Several PhD in astrophysics.
They didn't spend 30 years and 10B for a big jpeg don't worry
These pics are gimmicks sent to the public as a "see what we did". It's like if Armstrong personally brought you back a moon rock, you'd be like "yeah cool that's a rock" because you don't have the instruments to analyse it nor the knowledge to know what to even look for.
quintet: https://esawebb.org/images/weic2208a/zoomable/
https://esawebb.org/images/weic2208b/zoomable/
carina: https://esawebb.org/images/weic2205a/zoomable/
https://esawebb.org/images/weic2205b/zoomable/
Southern ring https://esawebb.org/images/weic2207a/zoomable/
https://esawebb.org/images/weic2207b/zoomable/
https://esawebb.org/images/weic2207c/zoomable/
It seems to negatively degrade the photos taken much more so than Hubble.
Also curious about what the closest stars to our solar system would look like. Of course it also makes me wonder what would we be able to see given a 100x increase in aperture. Like for example if we could send up something extremely large on Starship. Would we be able to image planets in our local group? Exciting!
Searching for this stuff is kind of hard (information overload), so I'm wondering if anyone here has more up to date info.
Summary: they can see it in the data, but events such as this were expected and part of the lifetime of the telescope.
I wanna see what this thing is able to do with a 10 days exposure. Let it loose.
Ever seen a solid white square? =)
As with all things, it totally depends on what's being imaged. Exposing the Orion Nebula for 10 days would result in a totally over exposed image looking like a solid white square.
I want the Webb focusing 10 days on a patch that looks pitch black on Hubble’s 10 days deep field
Re-read comment.
What am I missing?
You're making the assumption the poster meant they didn't have this feeling before. They might just be repeating that, once again, it's difficult to do this with Webb. Hubble is irrelevant. Anything else is irrelevant. They're talking about the pictures here in front of us.
I was absolutely agreeing with the sentiment. I clearly asked if the feeling was there before as well or if it was just from the new images.
Thanks for your charity though
High quality digital is clearly superior sonically, but vinyl has a dullness around the edges that is so aesthetically pleasing.
I agree that the Hubble images are just pleasant to look at, warm and wonderful.
What happens when it's pointed at Mars?
Ah found answer here
https://space.stackexchange.com/questions/57492/can-james-we...
Edit it could be because of my default zoom level https://news.ycombinator.com/item?id=32076048
[1]: https://en.wikipedia.org/wiki/File:Stephan%27s_Quintet_Hubbl... [2]: https://johnedchristensen.github.io/WebbCompare/img/Stephans...
It might be because of a different post-processing algorithm, or some phi-related magic, just curious a bit.
https://en.wikipedia.org/wiki/Diffraction_spike
>"...four spider vanes supporting the secondary mirror. These cause the four spike diffraction pattern commonly seen in astronomical images."
> > Hubble telescope was funded and built in the 1970s by the United States space agency NASA with contributions from the European Space Agency. Its intended launch was 1983, but the project was beset by technical delays, budget problems, and the 1986 Challenger disaster. Hubble was finally launched in 1990.
I commented on this other thread: https://news.ycombinator.com/item?id=32074242
This site has a diagram of the spectrum that shows which portions are covered by each telescope, as well as some video clips comparing photos captured by Hubble and Webb. The first video of the Lagoon Nebula (M8) demonstrates what I'm saying pretty well.
https://webbtelescope.org/webb-science/the-observatory/infra...
Very nicely done!
At this point I like it even for just brightening the news cycle anyway.
1. Can the telescope be pointed in any direction? (of course, orthogonal to the suns rays, I understand the need to cool it down).
2. If it can be pointed, I am assuming some boosters would be used to pivot it. How long do these last?
3. Is there any info on the orbit? Can the orbit degrade?
4. All the fluid / gas required to correct / point, can it be refilled?
https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-m...
2. Basically any satellite in use today uses spinning masses which it can speed up or down to change the direction it's looking. Angular momentum is conserved, but direction pointing isn't. Eventually due to uneven forces (eg, from the sun), these reaction wheels become "saturated" and some propellant is used slow the wheels down. Current estimates put the fuel running out in more than a decade.
3. It's an orbit in L2, past the Earth from the Sun's view. This orbit is unstable, and some of the fuel will also be used to maintain this orbit.
4. There is no refilling mechanism built in. It's likely once the propellant is out the mission will be done. There is the possibility of another spacecraft grabbing onto James Webb and pushing it for station keeping, but it wouldn't be able to refill it. One major innovation with the James Webb though is that it's refrigerator is closed loop, as otherwise running out of coolant would be the mission limiting factor.
Too bad, then, about the crappy colorizing/outlining for the 'so pretty' crowd. I await the site that simply shows (frequency-shifted) images. Any colorizing should have a 'legend' describing its purpose.
what's more interesting to me is what we can learn about exoplanets from this mission
https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-...
But apart from that, there's the raw data, which is surely somewhere in the public domain, but that's way less useful in communicating those achievements to the public.
https://hubblesite.org/contents/media/images/2008/34/2405-Im...
I'm not talking about just deleting the pixels. If you know your measurement instrument introduces artifacts, you just move it around or use some ground-truth image until you map the artifacts and then subtract them out by convolution.
Great work, it feels smooth and intuitive.
How about you?
This means: the AI has to predict what it is supposed to look like and for that we would need out of water pictures as reference in the first place which we didn’t so far!
And then: even if we have these new out of water pictures as reference, the AI generated ones would still not show what is real, but instead a fiction. The fiction can look believable but it cannot be studied to derive facts from it. It’s like trying to study an AI generated language.
This sounds like my friend who literally believes that buses will go extinct within 3-5 years as every vehicle will self drive. It’s not thought all the way through.