[HN Gopher] Compare Webb's Images to Hubble
___________________________________________________________________
Compare Webb's Images to Hubble
Author : hexomancer
Score : 1546 points
Date : 2022-07-12 18:41 UTC (1 days ago)
(HTM) web link (johnedchristensen.github.io)
(TXT) w3m dump (johnedchristensen.github.io)
| ijidak wrote:
| This is perfect! Without this context it's hard to appreciate how
| much better Webb is!
| boomskats wrote:
| The sliders break when page zoom is anything other than 100% :/
| mholt wrote:
| Here's a backyard telescope versus Webb:
| https://twitter.com/AJamesMcCarthy/status/154694183270093209...
|
| 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.
| dr_orpheus wrote:
| The spikes are caused by diffraction of light around the struts
| supporting the secondary mirror. Hubble has 4 supports for the
| secondary mirror. JWST has 3 support for the secondary mirror,
| which because...physics (I don't know I'm not an optics
| guy)...manifests as 6 diffraction lines.
|
| 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.
| timcederman wrote:
| Full explanation: https://stsci-
| opo.org/STScI-01G6933BG2JKATWE1MGT1TCPJ9.png
| WorldMaker wrote:
| Apparently the Diffraction spikes come from both the primary
| mirror shapes and the struts holding the secondary mirror.
| The primary mirrors of the JWST are hexagonal which would
| explain hexagonal looking effects. The three struts are
| apparently designed so that two of the struts match the
| hexagonal mirror angles at all times and are "hidden" inside.
| (The third strut apparently sometimes causes two much smaller
| "horizon" spikes for very, very bright objects.)
|
| Hank Green on TikTok did a neat, quick demonstration in video
| form.
| dr_orpheus wrote:
| Oh, thank you that makes sense. And due to the folding of
| the mirror and launch envelope constraints they can't
| equally space the three struts such that ALL are inside the
| diffraction of the hexagonal mirror.
| mintyLemon wrote:
| Link to that Hank Green video on YouTube:
| https://m.youtube.com/watch?v=Y7ieVkK-Cz0
| loxias wrote:
| The hero we need.
|
| Thanks!
| andai wrote:
| These these two pages have some nice visualizations of
| the optical phenomena:
|
| https://blogs.nasa.gov/webb/2022/02/03/photons-incoming-
| webb...
|
| https://bigthink.com/starts-with-a-bang/james-webb-
| spikes/
| hackernewds wrote:
| ah an authoritative source. if only we funded scientific
| exploration more heavily with public funds..
| kadoban wrote:
| They're not lens flares, but they're still an artifact of the
| system, which is probably what most people mean by "lens flare"
| anyway, due to lack of a better common term.
| JacobThreeThree wrote:
| According to the Wikipedia definition, I'd say that Webb's
| artifacts could be classified as "lens flares".
|
| >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.
|
| https://en.wikipedia.org/wiki/Lens_flare
| Cogito wrote:
| Diffraction spikes are caused before the lens gets
| involved; improving the lenses cannot remove the spikes
| (though there may be structures causing diffraction spikes
| in-between lenses).
|
| 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.
| JacobThreeThree wrote:
| >The spikes from JWST are primarily caused by the edges
| of the mirrors and the three support struts.
|
| That sounds to me like "light scattered by the imaging
| mechanism".
| m463 wrote:
| Actually I would say the effect mimics a "cross filter" /
| "star filter" special effect.
|
| https://en.wikipedia.org/wiki/Photographic_filter#Cross_scre.
| ..
| noisy_boy wrote:
| Which begs the question: is there a computational way to
| "collapse" the spikes in post-process? They are beautiful but
| also sort of distracting when you are trying to take in the
| enormous mass of stars in these photos.
| nullc wrote:
| deconvolution, but it's more art than science because the
| problem is ill conditioned and blows up without
| regularization-- particularly if any part of the spike is
| overexposed (which it usually as you only notice the spikes
| on extremely bright stars).
| foxhop wrote:
| thank you very informative.
| [deleted]
| Unklejoe wrote:
| I read at some point that a piece of dust hit the telescope and
| potentially damaged it. I'm guessing that it turned out not to be
| a big deal or maybe they were able to work around it? Does anyone
| have any insight? The fact that they're releasing good pictures
| and not mentioning it seems like a good sign to me.
|
| Searching for this stuff is kind of hard (information overload),
| so I'm wondering if anyone here has more up to date info.
| dtgriscom wrote:
| https://blogs.nasa.gov/webb/2022/06/08/webb-engineered-to-en...
|
| Summary: they can see it in the data, but events such as this
| were expected and part of the lifetime of the telescope.
| smohare wrote:
| Damn near unusable of mobile. Cool.
| causi wrote:
| Interesting that while they're certainly more detailed they also
| look "flatter" than the Hubble images. Is that due to differences
| in hardware or different choices in post-processing?
| thatswrong0 wrote:
| Just needs to include exposure time differences and this is
| perfect. Glad to witness the power of this fully armed and
| operational battle station.
| laserbeam wrote:
| It's my understanding that Webb used much shorter exposure
| times than Hubble, correct?
| akira2501 wrote:
| Exposure time on Webb is complicated. The sensors are
| different, the sampling techniques are different, and you can
| get the on board systems to do integration within sets of
| exposures for you.
|
| https://jwst-docs.stsci.edu/understanding-exposure-times
| tambourine_man wrote:
| Yes, hours vs days, which makes them a lot more impressive if
| you know a bit about photography.
|
| I wanna see what this thing is able to do with a 10 days
| exposure. Let it loose.
| dylan604 wrote:
| >I wanna see what this thing is able to do with a 10 days
| exposure.
|
| 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.
| tambourine_man wrote:
| I trust astronomers to know how to set the exposure.
|
| I want the Webb focusing 10 days on a patch that looks
| pitch black on Hubble's 10 days deep field
| nooyurrsdey wrote:
| This is a wonderful way to visualize side by side images like
| this.
|
| Great work, it feels smooth and intuitive.
| hparadiz wrote:
| I'm actually most looking forward to seeing a picture of our
| planets. I wonder what kind of resolution we'll get of Jupiter
| and Mars in particular.
|
| 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!
| svachalek wrote:
| We've got very good pictures of our own planets thanks to
| probes that did flybys. Maybe I'm way off but I'm pretty sure
| JWST won't be able to beat those. I also wonder if it can even
| handle that much light, I know it can't look at the moon or it
| will burn out.
| hparadiz wrote:
| Oh for sure it won't. I'm more interested in that as a tech
| demo.
| Balgair wrote:
| Imaging Phattie/IX would also be pretty cool. It's been a while
| since we've discovered a real big-boy planet.
|
| https://en.wikipedia.org/wiki/Planet_Nine
| jhoechtl wrote:
| The post-processing in the webb images is hilarious. Marketing at
| its best.
| mouzogu wrote:
| old and new images already looked highly processed, that
| photoshop look - which i think some of us got a little jaded on
| maybe.
|
| 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-...
| ygra wrote:
| Isn't that look mostly a mapping of the observed wavelengths
| into the visible spectrum? I think at least for some of those
| images the different colors correspond to different chemical
| elements, which makes for pretty images _and_ some extra data
| that's interesting. For purposes of comparison with Hubble
| images it would also make sense to process them in the same
| way.
|
| 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.
| mtlmtlmtlmtl wrote:
| I love this. But the Carina Nebula doesn't work on Firefox for
| Android. It just displays the JWST image.
| yellowapple wrote:
| For me it shows the top half of the Hubble version, but not the
| bottom.
| wlesieutre wrote:
| That's the extent of the Hubble original
|
| https://hubblesite.org/contents/media/images/2008/34/2405-Im.
| ..
| mtlmtlmtlmtl wrote:
| That makes sense then. I have two suggestions if the person
| who made this is reading: maybe fill out the hubble image
| with black so it can line up with the JWST image, might
| make the interface less janky? Or if someone knows of a
| larger imagine from another telescope(Spitzer?) That could
| be a more interesting comparison for that particular
| observation.
| red_trumpet wrote:
| Changing the orientation of my phone from portrait to landscape
| while on the site somewhat solved this.
| TeeMassive wrote:
| Notice how the Southern Ring Nebula has expanded
| sharmin123 wrote:
| d--b wrote:
| These need to be adjusted for brightness... The Hubble ones are a
| lot darker which make things harder to spot.
| dtgriscom wrote:
| I just filed an issue on the project. (Gotta look that gift
| horse in the mouth...)
| protoster wrote:
| Bug report: On Firefox the difference wiper thing doesn't appear
| for the last image (Carina Nebula), it only shows the full Webb
| image.
| weaksauce wrote:
| funny enough that one didn't work on chrome but worked in
| firefox nightly albeit a distorted version that only showed the
| top left corner of it... I'm not sure hubble shot the full
| version?
|
| https://i.imgur.com/oBK3sWE.png
| ask_b123 wrote:
| I'm seeing the same and I assumed that Hubble hadn't shot the
| full version.
| nathancahill wrote:
| Working on latest FF on Mac. The Hubble image is just smaller.
| mastazi wrote:
| on Brave, instead it's the polar opposite, only the Carina
| Nebula works
|
| Edit it could be because of my default zoom level
| https://news.ycombinator.com/item?id=32076048
| deepzn wrote:
| The Carina Nebula is the most amazing photo. The level of detail
| now shown by JWST is breathtaking.
| nabakin wrote:
| I think so too. I even made another comparison website for it
| because OP's website doesn't use the full resolution images.
| Each image is about 50 MB so it will take awhile for it to
| load.
|
| https://hubblevwebb.tiiny.site
| bandyaboot wrote:
| I'm curious what's going on in the upper left area of the Carina
| Nebula image. The dust can't have actually cleared out that much
| since the Hubble shot was taken, could it?
| dylan604 wrote:
| Lots of visible light is reflected in the Hubble image from the
| dust causing it to look like it does. As others have said, the
| JWST does not suffer from that as it "sees" past those
| frequencies revealing new details instead.
| CitizenKane wrote:
| I believe the Hubble shot is more in the visible spectrum
| whereas the JWST images are in infrared so there are structures
| in each shot that don't necessarily show up in the analogous
| image.
| treesknees wrote:
| I'm not an expert, but from what I came across online earlier,
| the Hubble telescope sees more of the visible/UV spectrum than
| the Webb telescope. So it may just be a difference in what's
| captured.
|
| 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...
| pkaye wrote:
| With infrared you can see through the dust.
| xenadu02 wrote:
| Indeed - that's one of the primary reasons to build the JWT:
| Dust and gas blocks our view in various cases so we want to
| take images in wavelengths that are more transparent to that
| debris.
| wanderingstan wrote:
| Amazing! Would be interesting to also compare with earth-bound
| telescopes, to really appreciate the progress.
| prohobo wrote:
| Is it absurd to think that maybe the Carina Nebula's shape has
| visibly shifted a bit since the last photo?
| tonymet wrote:
| what's the practical application ?
| Balgair wrote:
| Of astronomy?
| tonymet wrote:
| of the James Webb Telescope
| irrational wrote:
| Hmm, for some reason I prefer Hubble's image of Stephan's Quintet
| over JWST's. Though, that is purely from an aesthetic
| perspective. I am sure JWST's is much more impressive from a
| scientific standpoint.
| kumarvvr wrote:
| So, I have a few questions.
|
| 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?
| Bjartr wrote:
| For 2, JWST uses reaction wheels to manage it's orientation.
| These are just heavy wheels it spins faster or slower to change
| it's own angular momentum.
|
| https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-m...
| Laremere wrote:
| 1. It can be pointed at any direction, just not at any time. It
| actually can't look directly away from the sun either, just to
| the sides. See https://jwst-docs.stsci.edu/jwst-observatory-
| characteristics...
|
| 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.
| baltimore wrote:
| Now build a zoomable full-res version. Because I am spoiled and
| want the internet to do things for me.
| yread wrote:
| ESA got your back:
|
| 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/
|
| Deep field https://esawebb.org/images/weic2209a/zoomable/
|
| https://esawebb.org/images/weic2209b/zoomable/
| mrleinad wrote:
| Well, I found my next set of ultrawide wallpapers for my 49"
| monitor :) Thanks!
| mtlmtlmtlmtl wrote:
| Not a UI or web guy scaling the slider with zoom might do the
| trick?
| nabakin wrote:
| I made a full-res version for the Carina Nebula. Not sure how
| to make it zoomable on desktop (it's zoomable on mobile).
|
| https://hubblevwebb.tiiny.site/
| ck2 wrote:
| Will Webb ever be used to image our own planets?
|
| What happens when it's pointed at Mars?
|
| Ah found answer here
|
| https://space.stackexchange.com/questions/57492/can-james-we...
| angryGhost wrote:
| born too early...
| echelon wrote:
| For the machines that will replace us.
| suddenexample wrote:
| It's a bit ironic that to me, the layman, Hubble's space images
| have been so ubiquitous that Webb looks kind of... posterized.
| For example, in that last comparison of the Carina Nebula, Hubble
| has that ethereal quality that so many space pictures do, whereas
| Webb's crispness reminds me almost of a drawing.
| temptemptemp111 wrote:
| bastardoperator wrote:
| Downvote me to hell, but as a person who has zero understanding
| of what differentiates Hubble from Webb, the pictures alone just
| aren't doing it for me. I was excited to see something completely
| new given 30 years and 10 billion dollars and instead I feel like
| I'm seeing what looks like an enterprise upgrade and feel
| slightly disappointed.
|
| What am I missing?
| Mangalor wrote:
| These are just the first few images. Give it time.
| SiempreViernes wrote:
| That's somewhat fair, but Hubble and JWST have fundamentally
| pretty similar resolutions so JWST will never get hugely
| better.
|
| 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.
| thatswrong0 wrote:
| TBH, I don't think the photos were ever going to be that much
| more groundbreaking to your average person, given the fact that
| the angular resolution of the telescope is roughly equivalent
| to the Hubble.
|
| 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.
| [deleted]
| sandgiant wrote:
| The JWST is only now entering science operations. What you see
| is pretty pictures taken as part of the commissioning and PR
| efforts of NASA.
|
| 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....
| bryananderson wrote:
| Webb isn't optimized to produce maximally pretty pictures,
| because most of Webb's groundbreaking science is not
| necessarily going to involve pretty pictures. For example, Webb
| will tell us otherwise-unknowable things about the atmospheric
| composition of exoplanets--but it will not produce stunning
| photos of them (too small and far away to look like more than a
| pinpoint). Webb will tell us discipline-defining things about
| the cosmological conditions in the very earliest years of the
| universe--but that doesn't mean it can show us pictures of the
| earliest galaxies in the same close-up detail as it could of a
| nearby galaxy. The latter image, while more breathtaking for us
| laypeople, would not tell us much of anything new.
|
| 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.
| nullc wrote:
| It took a while even once Hubble was fixed for people to
| figure out the processing to extract the prettiest pictures
| from it.
|
| 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/Pil
| lars_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.
| tiborsaas wrote:
| Detecting alien life has now become reality, JWST can analyze
| the composition of exoplanet atmosphere. If we can detect any
| technosignatures, then we made the discovery of the millennia.
| nirui wrote:
| Not an expert. But we are inside a galaxy ourselves, and it's
| not easy to leave this place. The scenery around us gets dated
| really quickly once we saw it for the first time, and it will
| probably stay boring until we visit another part of the
| universe to change the view.
|
| 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).
| echelon wrote:
| I can understand this sentiment, but I'm excited by the results
| we _won 't_ see: chemical spectra.
|
| 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.
| oldstrangers wrote:
| What you're missing is the science and all the new data we'll
| find with an infrared telescope, which will come down the road.
| Yes it takes cool pictures, but that's just a bonus. JWT's real
| function is to facilitate hard science.
| stevage wrote:
| With respect, the goal of a major scientific project is not to
| impress the layperson with pretty pictures.
| kmano8 wrote:
| Though of course the pretty pictures really help with
| increasing the appetite from the public for spending on
| projects like this.. and capturing people's imaginations is a
| necessary part of the long game.
| greenbit wrote:
| This thing can see through dust. That's pretty cool, don't you
| think?
| SkyMarshal wrote:
| The TLDR is that Webb can see much further across the universe
| (and thus much further back in time) and at higher higher
| resolution than Hubble, and Webb's primarily Infrared sensors
| can see through nebulae, space dust and other obstructions
| better. There are numerous videos on the differences, but here
| are some I found pretty good:
|
| 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
| prawn wrote:
| I thought this comparison was pretty impressive:
|
| https://twitter.com/Batsuto_/status/1546900387931766784
| fleddr wrote:
| Pretty expensive Insta filter.
| _benj wrote:
| just WOW! I always feel so tiny when considering the absurd
| dimensions of space brought shockingly vivid with this images!
| mihaic wrote:
| I do like that this is generating interest and optimism for
| science again, yet I have yet to hear a good answer on what new
| insight we can expect from the lifetime of the telescope. Does
| someone have a good list of questions we're hoping to get better
| answers for?
|
| At this point I like it even for just brightening the news cycle
| anyway.
| supernova87a wrote:
| For the professional (or former professional) astronomers among
| us, I will make my somewhat amused observation that what people
| are most paying attention to is not really the distinguishing
| features of JWST.
|
| 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.
| nabla9 wrote:
| >The new thing is observations in the IR,
|
| 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)
|
| Hubble had ~40% of the Herschel's collecting area and Herchel
| had 40% of the JWST's collecting area.
| tigershark wrote:
| The increased resolution is extremely important given that the
| diffraction threshold is function of the wavelength and the
| mirror diameter. And you can clearly see that in the MIRI
| images at a longer wavelength that have a noticeably lower
| resolution compared to Nircam. If Webb mirror was as big as
| Hubble the resolution would have been bad in the long
| wavelengths. Hubble couldn't have had a better resolution with
| better instruments, he was already limited by its aberration
| problem and the new instruments were designed to mitigate that
| problem.
| supernova87a wrote:
| Those are good points -- my original comment was a little
| simplistic.
|
| I don't have the info at hand -- do you know what was the
| resolution of HST optical/NIR imagers versus JWST new
| imagers?
| nacogo wrote:
| Agreed! In the SMACS 0723 image, there is a red spiral galaxy
| near the top right which is effectively not present in the HST
| image because it was redshifted out of the spectrum. This
| implies it's one of the galaxies receding the fastest from us
| in the image right? And therefore also among the oldest and
| farthest away?
|
| https://blog.wolfd.me/hubble-jwst/
| lisper wrote:
| Yes, exactly right. (AFAIK, IANAA)
| t3estabc wrote:
| supernova87a wrote:
| Yes, well 2 possible effects:
|
| 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.
| mortenjorck wrote:
| Related question: to confirm, some of the additional detail
| we're seeing in the JWST images is in fact IR that has been
| "hue clamped" into the visible spectrum?
| soulofmischief wrote:
| It's all IR. It's color-mapped over RGB, but the sensors
| are IR.
| rkagerer wrote:
| Didn't the observed light shift into IR wavelengths due
| to the expansion of space over the last billions of years
| while it traveled to us?
|
| Do the recolored images have any relation to what the
| original view would have looked like, or is it just
| arbitrary "artistic license"?
| supernova87a wrote:
| Hey, that's an interesting and uncommon question that I
| had not seen elsewhere --
|
| 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")
| credit_guy wrote:
| A tangential question. If these galaxies are so much
| redshifted, then they are probably very, very far. Like
| more than 1 billion ly far. And if that is so, they
| should look exactly the same today, tomorrow, in one
| year, or in a hundred years. If for some reason we wanted
| these images in much higher resolution, could we just
| point the camera to the same spot and take millions of
| shots and then apply a super-resolution algorithm?
| supernova87a wrote:
| I believe that in the image assembly pipelines for
| processing these astronomical images, they already do
| take into account / use the "dithering" patterns that
| you're hinting at. (Often the telescope will be pointed
| in a pattern with sub-pixel offsets over multiple
| exposures to do exactly this).
|
| 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... )
| soulofmischief wrote:
| Thanks for the write-up! It's definitely important to
| mention the single-channel aspect of the sensors because
| I guess many people probably don't understand that.
| dwringer wrote:
| The typical digital camera of today works the same way,
| just with 3 filters (R, G, B) kind of like a CRT pixel
| array in reverse[0].
|
| 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).
|
| [0]https://en.wikipedia.org/wiki/Bayer_filter
|
| [1]https://en.wikipedia.org/wiki/Tetrachromacy
| [deleted]
| jhugo wrote:
| Looked like from what perspective? A human eye on Earth?
| arjvik wrote:
| OP clearly means from an observer moving at
| (approximately) the same velocity as the object emitting
| the light.
| 9991 wrote:
| The objects aren't really moving in that sense. The
| expansion of space over time is what stretches the light.
| jhoechtl wrote:
| Without a fixed point of reference, what is the
| difference?
| 9991 wrote:
| The difference is the expansion of space is accelerating
| over time. And certain wavelengths of light will be
| blocked by gas in the intervening space, and which light
| is blocked changes over time based on how red-shifted it
| is. Special Relativity isn't enough to explain this.
| wlesieutre wrote:
| NIRCam's range starts at 0.6 microns (600 nm) so picks up
| a little bit of the red end of our visible range. But it
| definitely can't differentiate a range of human visible
| colors.
| drbw wrote:
| Astrophysicist YouTuber Dr Becky covered this last month:
| https://www.youtube.com/watch?v=sNJR3lenz1I
| Cthulhu_ wrote:
| If I may get political here (nothing personal / no direct reply
| to the parent comment):
|
| > 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?
| dtgriscom wrote:
| Public support for NASA drives the members of Congress to
| allocate funds for its work. So, NASA spends a whole lot of
| effort showing the public how cool its work is. That, and it
| divides its facilities and subcontractors across the various
| states to ensure that every member of congress has
| constituents who benefit from its payroll.
| TulliusCicero wrote:
| Yeah, more or less. People gripe about it occasionally,
| especially on the left, but then some shit will go down like
| Ukraine and suddenly nobody wants to look like an idiot
| (which will absolutely happen in an American context if you
| suggest cutting military spending right after Russia invades
| someone).
| neuronic wrote:
| >$700B
|
| 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?
| dQw4w9WgXcQ wrote:
| > is there public support for the >$700B a year spent on the
| military?
|
| 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.
| snowwrestler wrote:
| It's not so much public support as the lack of public
| opposition.
|
| 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.
| AQXt wrote:
| > especially since the images are stylized / colored anyway
|
| 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.
| tiagod wrote:
| I don't think that's on purpose
| ygra wrote:
| It's not an effect. It's a diffraction artifact that's a
| consequence of the telescope construction. Explained here for
| example: https://bigthink.com/starts-with-a-bang/james-webb-
| spikes/
| MeteorMarc wrote:
| Although this reference nicely explains the origin of the
| diffraction pattern on the JWT images, it does not explain
| why the spikes seems to extend much farther then in the
| Hubble images. My hunge is that the JWT succeeds much
| better to gather all the light into a real point which
| makes the primary diffraction pattern stronger too.
|
| 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.
| ElThomaso wrote:
| In the second image it is clear that more of the nebula is
| visible, isn't this because more wavelengths of light are being
| detected? In this case an amateur absolutely can appreciate the
| technical improvements, the IR is mapped to a visible RGB
| spectrum...
| svachalek wrote:
| Different wavelengths. The JWST also cannot see the shorter
| wavelengths that Hubble excels at.
| undersuit wrote:
| I'm impressed by the speed of the imaging. Apparently the
| Hubble Deep Field took over 10 days of telescope time while
| JWST did it in 12.5 hours.
| libraryatnight wrote:
| supernova87a wrote:
| Apologies, I did not mean for it to come off that way. I
| edited it to not make such broad brush statements.
|
| 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.
| jsjohnst wrote:
| > I'm sure you were well intentioned, but this comment read
| all kinds of rude and negative.
|
| Pot, meet kettle. Except you are flat out an arse while GP
| was mostly innocent in their action I feel.
| Ensorceled wrote:
| > This is so dismissive and insulting. ... I'm sure you were
| well intentioned, but this comment read all kinds of rude and
| negative.
|
| 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."
| Enginerrrd wrote:
| I think this is a little harsh, but I actually generally
| agree. I'm a total laymen here and my PRIMARY TAKEAWAY has
| been the IR component and how much more and further away you
| can see because of it.
| Ensorceled wrote:
| I get what you are trying to say here, but someone posting
| on HN about "the IR component" using the nom de guerre
| "Enginerrd" might not be "a total laymen" :-)
| Enginerrrd wrote:
| Ok, yeah, in retrospect that's probably fair.
| gliptic wrote:
| > HST might have done that if its instruments had been of
| different pixel size or imaging array size / focal length
|
| HST is already imaging at diffraction-limited resolution (with
| proper post-processing). It would need a bigger mirror to get
| there.
| jstgord wrote:
| .. and why is infra-red more useful ? Can we see through dust
| or something ?
| bryananderson wrote:
| Seeing through dust is part of it. Another part is redshift:
| because of relativity, things moving away from us appear
| redder (longer wavelength) the faster they're moving away.
| That's the same principle (Doppler effect) as the lower-
| pitched siren sound as the ambulance drives away. Because the
| universe itself is expanding, the farther something is from
| us, the faster it's moving away relative to us, and the more
| redshifted it appears to us. And again because of relativity,
| the oldest objects we can see are the ones that appear
| farthest away (i.e. their light is just now getting here,
| after 13 billion years, from 13 billion light years away).
| Thus, if we want to study the earliest times of the universe,
| we must study the most redshifted objects--which have shifted
| all the way out of the visible spectrum and into the
| infrared. Hence, Webb is an infrared telescope.
| dotancohen wrote:
| Your statements about redshift and distance are correct,
| but I do not see where relativity comes into it. Even in
| Newtonian physics redshift occurs. If you could elaborate I
| would love to learn. Thank you!
| sushibowl wrote:
| Newtonian physics does have the Doppler effect which can
| cause red shift, but it doesn't accurately explain the
| red shift that occurs when observing distant galaxies.
| That's because this red shift occurs due to three
| factors:
|
| 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.
| dotancohen wrote:
| I see, thank you.
| bryananderson wrote:
| Yeah, you're correct, you don't need to invoke relativity
| to explain the Doppler effect. Sibling comment did a good
| job explaining the ways relativity does impact redshift,
| but my initial statement ("because of relativity...") was
| not correct.
| jcims wrote:
| Look how much more transparent the dust is in the carina
| image at the bottom:
|
| https://johnedchristensen.github.io/WebbCompare/
| foobarbecue wrote:
| Infrared is the only way to see things that are cold (as in
| not a star) or extremely far away (due to redshift).
| skybrian wrote:
| What about reflected light, like most things we see in the
| solar system?
| foobarbecue wrote:
| Good point, I shouldn't have said "only." I have heard of
| reflected light been used for exoplanet observations
| although I think it's quite faint. I guess some nebulae
| are illuminated by stars. I don't know if the reflected
| light is longer wavelength than the incident light, but I
| suspect so. BTW I'm not an astronomer!
| mtlmtlmtlmtl wrote:
| Right. After the initial "wow factor" has settled down, what's
| been most striking to me is the level of detail that's no
| longer obscured by gas and dust in these nebulae due to MIRI. I
| know very little about the study of stellar nurseries or
| planetary nebulae but I've seen enough pre-JWST images of them
| to know that astrophysicists just got a whole lot to sink their
| teeth into and I look forward to seeing further developments as
| more data is collected and existing data is studied.
| Helmut10001 wrote:
| Well, also, one thing to note is that it took WEBB only hours
| to capture these images, while HUBBLE was aimed for days and
| months to capture comparable ones. It will be interesting to
| see the results when they have more time to capture longer
| sequences of light.
| Centmo wrote:
| Also, when comparing the deep field images I don't think it can
| be stressed enough the difference in exposure time between HST
| and JWST images (Hubble had a 10x longer exposure time). Many
| many more distant galaxies would become visible in the JWST
| image with the much longer exposure time. I look forward to
| seeing some long-exposure deep field images from JWST!
| kibwen wrote:
| This is underappreciated. Much lamentation has been made of
| the fact that JWST's current mission length is only ten years
| (maybe twenty or thirty at best, but hard-limited by on-board
| coolant), but with the speed of its observations that ten
| years will be as productive as a century of Hubble time.
| MichaelZuo wrote:
| It's difficult to imagine how more detailed the JWST images
| could be if they used the same observation time as the
| Hubble images.
|
| Will there be thousands of additional extremely red shifted
| galaxies?
| antisthenes wrote:
| With a 10x observation time, you would probably be
| approaching a uniform cosmic background of multitudes of
| 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.
| [deleted]
| matesz wrote:
| Did anybody make a comparison for rough estimation on the number
| of galaxies in the observable universe based on hubble vs webb?
| Helmut10001 wrote:
| Strange, when I compare the two images of Stephan's Quintet [1],
| it appears much more "progressed" in the new WEBB image [2]. But
| that should be impossible.
|
| [1]:
| https://en.wikipedia.org/wiki/File:Stephan%27s_Quintet_Hubbl...
| [2]:
| https://johnedchristensen.github.io/WebbCompare/img/Stephans...
| dan_mctree wrote:
| Overlaying them, it seems the JWST images have brighter galaxy
| edges and gas. This makes the galaxies look bigger, which in
| turn could make it appear as if the galaxies are closer
| together. Is that what you mean with 'progressed'?
| Helmut10001 wrote:
| Yes, I think you're right - also, the linked HUBBLE image
| from wikipedia is rotated a bit, which increases the effect
| that two of the 5 galaxies appear to be closer together in
| the WEBB image.
| eevilspock wrote:
| Are the four vs six point starbursts an artifact of the different
| lens / mirror designs? The Webb telescope has hexagonal mirrors,
| but not sure about Hubble.
| woevdbz wrote:
| It's striking how much more flamelike the structures appear to
| be, with the added resolution
| WalterBright wrote:
| My God, it's full of stars!
| SCAQTony wrote:
| Aesthetically, I like the Hubble images better, they are more
| painterly and colorful. However there is no doubt that the JWST
| contains way more information and is exponentially more valuable.
| codq wrote:
| It's kinda like listening to music on vinyl vs. digital.
|
| 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.
| tmm84 wrote:
| I'm glad someone here said this about them. I grew up seeing
| Hubble style images (non-IR) so I get the warm fuzziness they
| have. For me the one thing that gets me are the big shiny stars
| that seem to have big streaks going everywhere. They feel like
| lens flare in the photos.
| izacus wrote:
| Ummm, pretty much all of those images are artificially colored
| so your comment basically just judges the person postprocessing
| the images and applying colors for detected wavelengths.
| rnmp wrote:
| It's as if they remastered an old video game. So much more
| detail!
| avelis wrote:
| To touch the stars. To reach a galaxy. To dream of afar. And in
| the deepest space, see our ancestry.
| throwaway4837 wrote:
| It's hard to look at the Webb images without thinking that
| there must be life and technology out somewhere else in the
| stars.
| quickthrower2 wrote:
| Reading the selfish gene is making me think the same thing.
| dylan604 wrote:
| Why does that only come from Webb images? You weren't getting
| that same sensation looking at the Hubble images before? If
| that's true, then welcome to the club! It took you a bit
| longer, but we're happy you're here now. ;P
| throwaway4837 wrote:
| > Why does that only come from Webb images?
|
| Re-read comment.
| dylan604 wrote:
| "It's hard to look at the Webb images without
| thinking..."
|
| What am I missing?
| scrollaway wrote:
| A charitable interpretation.
|
| 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.
| dylan604 wrote:
| cheap shot?
|
| 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
| 8bitsrule wrote:
| The new scope appears to be capable of wonderful images, and no
| doubt many new discoveries.
|
| 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.
| mihaic wrote:
| Does someone have any intuitive explanation on why Hubble images
| for bright stars seem to have a cross-shaped lens-flare effect,
| while for JWT it's got six spikes?
|
| It might be because of a different post-processing algorithm, or
| some phi-related magic, just curious a bit.
| cainxinth wrote:
| I believe the six spikes from JWST are because of its hexagonal
| mirror segments.
| FourHand451 wrote:
| This was my guess as well, but if it's correct, I don't
| understand why the Hubble images show 4 spikes. I thought
| Hubble's main mirror was circular, not a square.
| cainxinth wrote:
| As usual, wiki has the answer:
|
| 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."
| justanotherme wrote:
| A question to the experts here: What will be the most exciting
| things to be explored within the next months? What insight could
| come out of it, which open questions could be answered? Hints to
| life on other planets by observing specific spectrums of specific
| ones? Could certain open questions about the early universe be
| decided? Or something else?
| sandgiant wrote:
| What you find most exciting is a subjective thing. I don't have
| a clear answer, but you can browse through the list of accepted
| proposals in cycle 1 and decide for yourself:
| https://www.stsci.edu/jwst/science-execution/approved-
| progra....
| anigbrowl wrote:
| I'm slightly surprised they haven't gotten rid of the stellated
| hexagon artifacts with software.
| mordae wrote:
| And replace them with what?
| anigbrowl wrote:
| Nothing, that's kinda the point.
|
| 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.
| jauntbox wrote:
| Very cool to see several galaxies that were entirely invisible to
| Hubble due to high redshift show up brightly to JWST.
| systemvoltage wrote:
| > This makes the Hubble telescope even more impressive in my
| eyes. Built 50 years ago with presumably 60 year old tech.
|
| > > 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
| jcims wrote:
| Advantages of IR incredibly apparent in the last pic.
|
| Very nicely done!
| acqbu wrote:
| Hubble = iPhone 4S; Webb = Galaxy S22 Ultra
| UberFly wrote:
| Considering these are just the initial "test" images there is
| going to be some amazing stuff to come over the years. Can't
| wait.
| somenewaccount1 wrote:
| Thank you so much!!! I really wanted to see the difference side
| by side and this was an even better presentation. Really cool!
| hexomancer wrote:
| Just to be clear I did not create this website, I just saw it
| on reddit. All credits to the original author:
| https://www.reddit.com/r/woahdude/comments/vxeeqo/i_made_a_t...
| dynm wrote:
| Question for anyone who happens to be an expert: Is there any way
| to quantify how much better Webb is independently of the amount
| of time used to take the exposures? Like, could Hubble achieve
| the same quality of images as Webb if it was given 100x (or
| whatever) more time exposure?
|
| 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?)
| spenczar5 wrote:
| I worked in astronomy software for a few years for a different
| telescope, the LSST. I am not an expert, but I was in this
| world enough to answer.
|
| 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.
|
| Now - this was all about how _many_ photons you collect. When
| humans look at an image, they also care a lot about how fine
| the details are on it. This has to do with the resolution of
| the telescope 's imaging systems. Resolution is limited by the
| number of pixels on the detector, and (to a much lesser extent)
| by the optical train of the telescope - the aberrations and
| distortions introduced by mirrors that focus light onto the
| detector's pixels.
|
| 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.
| mtlmtlmtlmtl wrote:
| IANA{astrophysicist, space engineer} but I do follow this
| closely and have what I call a working armchair understanding
| of this stuff. Anyone from relevant fields is welcome to gently
| correct any imprecisions. I always want to learn more and will
| thank you for it
|
| >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...
| lttlrck wrote:
| Plus, upgrading Hubble wouldn't get us close either. JWST is
| specifically designed to shield the sensors from IR/heat, and
| it's 1 million miles from Earth for a similar reason.
| gcbirzan wrote:
| > 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.
|
| It's a matter of speed not distance, isn't it?
| mpcjanssen wrote:
| Redshift is indeed a matter of speed. But due to the
| expansion of the universe, relative speed and distance are
| directly related (Hubble's law).
|
| 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.
| ozzydave wrote:
| It's both, but the contribution from distance will be much
| greater than from the relative speed for an old, distant
| galaxy.
| jekdoce wrote:
| As I understand it redshifting is due to the doppler
| effect, whose formula only depends on the relative speed
| between the observer and the sender.
|
| However, it also seems like due to galaxies further away
| having a larger expansion speed, typically they are more
| redshifted.
| nomel wrote:
| > That is ~6.25 times the light collection area of
| Hubble(25.4m2 vs 4m2)
|
| 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).
| mtlmtlmtlmtl wrote:
| Right, that didn't occur to me at first, but is just
| obviously true when you point it out, thanks. Though I
| didn't know that hubble is actually higher resolution in
| that comparison.
|
| 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?
| dtgriscom wrote:
| The resolution is limited by the diameter, not the area
| (although they're usually closely linked).
| dylan604 wrote:
| No, expsoure time is not enough. Resolution is a factor of the
| size of the primary mirror. Exposure time just allows capture
| of photons at that resolution. With the JWST primary mirror
| dwarfing the Hubble's, then it will always have better imagery.
| 0xfaded wrote:
| Wavelength is also a factor. Huygens optics has a great video
| on this. tldr; angular resolution is about the same as the
| Hubble.
|
| https://youtu.be/gOpbXBppUEU
| red_trumpet wrote:
| I'm no expert either, but I imagine that high exposure times
| come with more motion blur. So just cranking up exposure time
| does not necessarily result in better pictures.
| dredmorbius wrote:
| There's effectively _no_ motion blur visible.
|
| 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.
| IshKebab wrote:
| Motion of what?
| dontlistentome wrote:
| everything everywhere all at once
| spookthesunset wrote:
| Minor changes to the satellite position? Vibration from
| some hardware? I dunno but the parent asks a question I ask
| too.
|
| 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.
| adgjlsfhk1 wrote:
| long exposure images aren't actually 1 continuous
| exposure. you take a ton of individual images and
| composite them using known reference points.
| ryneandal wrote:
| Well I mean the JWST is in orbit both around the L2 point
| and the sun. It's sensitive equipment must also be facing
| away from the sun. So there's a lot of movement going on
| out there.
| dylan604 wrote:
| I'm sorry but no no no. These telescopes are tracking the
| objects they are imaging specifically to avoid imaging issues
| from motion. This isn't some dude in the backyard with an
| alt-az scope bought from a Sears catalog.
|
| I really hope you were trolling with this response
| ryneandal wrote:
| Here's out exposure time works for JWST: https://jwst-
| docs.stsci.edu/understanding-exposure-times
| pythonguython wrote:
| Not an expert, but one metric to demonstrate Webb's capability
| is that Hubble's deep field exposure took 10 days, and Webb did
| it in 12.5 hours.
| mtlmtlmtlmtl wrote:
| This is true, but he was asking specifically about a metric
| that's independent of the exposure time.
| unethical_ban wrote:
| Webb's physical dimensions are larger than Hubble's. The
| "collecting area" of Web is 273 sq ft to Hubble's 46, per
| Wikipedia. The two telescopes are sensitive to different (but
| somewhat overlapping) bands of light. Hubble worked through the
| visible spectrum while JWST is almost exclusively infrared.
|
| 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.
| boloust wrote:
| The Hubble image of SMACS was a 10 day exposure, the Webb image
| was a 24hr exposure and is far superior.
| rdsubhas wrote:
| A crude analogy is like this: Two cameras are pointed towards a
| wall. Camera #1 is good, but it is blocked by the wall. Camera
| #2 has a special trick, it does some magic that can look behind
| the wall.
|
| 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.
| Osmium wrote:
| Regardless of exposure, you have to consider wavelength. There
| are some things JWST can see that are completely invisible to
| Hubble, or, similarly, there are objects that are opaque to
| Hubble that JWST can see right through. Just look at all the
| extra stars that appear in the image of the Carina Nebula for
| an example of that.
| agrajag wrote:
| For the wavelengths that the telescopes are designed to observe
| (primarily ultraviolet & visible for Hubble, though it can do a
| little bit of infrared, while JWST looks at Infra-red and mid-
| infrared) resolution is fairly comparable, though JWST has a
| much wider field of view and doesn't half to sit idle when it
| orbits the sun side of the earth like Hubble does.
|
| 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.
| masterspy7 wrote:
| Not trying to underscore this incredible achievement, but I'm
| curious if we could use AI techniques to upscale the Hubble
| images to achieve similar results as the Webb telescope. Has this
| been tried before?
| wetpaws wrote:
| No
| prawn wrote:
| For what purpose? If you wanted glorious and infinitely
| zoomable imagery without much concern for accuracy, couldn't
| you just design that? Marvel movies do that now. We already
| have artists' impressions in space articles and documentaries.
| lynguist wrote:
| It's a valid thought, but it would really be like trying to
| take pictures of the sky from underwater and using AI to make
| it look like it was taken from out of water.
|
| 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.
| Balgair wrote:
| Like, I guess you could run images and tensors through a
| neural net and see what the weights look like. That might
| tell you something that the endless pool of astro-grad
| students missed. Like, maaaaaaaybe you might have backed out
| dark matter from some strangely weighted neuron, or there
| might be something lurking in the noise that was missed. But,
| I really really doubt it.
| detaro wrote:
| AI upscaling works if you want a prettier picture, but not if
| you want to actually _know_ more. AI can 't magically conjure
| information that isn't there, so if you upscale it has to
| invent details to fill in. Which is fine for some use cases,
| but not for science or truth-finding.
| Kelm wrote:
| Sure you could try, but without getting real higher fidelity
| photos you'd never know how realistic the synthetic images are.
| [deleted]
| alberth wrote:
| Why is there so much more lens flare on Webb vs Hubble?
|
| It seems to negatively degrade the photos taken much more so than
| Hubble.
| Dave_Rosenthal wrote:
| The segmented design of the mirror creates diffraction effects
| vs. Hubble's single mirror.
| kristofferR wrote:
| This is a great explanation: https://bigthink.com/starts-with-
| a-bang/james-webb-spikes/
| libraryatnight wrote:
| This is interesting, thank you - going to pass this along to
| friends who were curious and got less informative answers :)
| FloatArtifact wrote:
| How much and what type post processing are appled to these type
| of images?
| mordae wrote:
| Most importantly the light frequencies have been mapped to
| visible spectrum.
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