NASA Releases Ridiculously Sharp Webb Space Telescope Images (gizmodo.com) 96
During a press conference Monday morning, NASA provided an update on the status of the Webb Space Telescope and released images from the telescope that put Webb's progress on dazzling display. Gizmodo reports: "I'm delighted to report that the telescope alignment has been completed with performance even better than we had anticipated," said Michael McElwain, a Webb observatory project scientist at NASA's Goddard Space Flight Center, in a NASA press conference. "This is an extraordinary milestone for humanity." Webb sits at an observational point called L2 nearly 1 million miles from Earth, where it will look further back in time than the Hubble Space Telescope. (Hubble will continue to operate alongside Webb once the latter is operational). [...] The preparation and testing of the telescope's science instruments (a process called commissioning) will take about two months to complete. Only once the commissioning is complete can Webb begin taking the scientific images that will define its tenure in space.
But some images are already being collected, to make sure the telescope is functioning properly. Webb's coldest instrument -- the Mid-Infrared Instrument (MIRI) -- recently took a test image of the Large Magellanic Cloud, a satellite galaxy of the Milky Way that was previously imaged by the now-retired Spitzer Space Telescope's Infrared Array Camera. Webb's image of the same region makes Spitzer's look like a finger painting, showing interstellar gas clearly distributed across the star field. The stars -- blots, in Spitzer's view -- are seven-pointed beacons of light in the MIRI test.
Webb's next steps will focus on taking images of its science targets, known as early release observations. These will not only be the first images of Webb science targets, but they will be the first images processed into full color. (Webb sees the cosmos in the infrared and near-infrared wavelengths, but the images will be translated into visible light.) Klaus Pontoppidan, a Webb project scientist at the Space Telescope Science Institute, said in the briefing that the chief differences between the most recent images and the ones to come are that the former were taken to test the telescope's ability to see clearly, whereas the latter will test the telescope's ability to image science targets. Pontoppidan wouldn't elaborate on what Webb team will capture in the early release observations -- the targets are a "surprise," he said.
But some images are already being collected, to make sure the telescope is functioning properly. Webb's coldest instrument -- the Mid-Infrared Instrument (MIRI) -- recently took a test image of the Large Magellanic Cloud, a satellite galaxy of the Milky Way that was previously imaged by the now-retired Spitzer Space Telescope's Infrared Array Camera. Webb's image of the same region makes Spitzer's look like a finger painting, showing interstellar gas clearly distributed across the star field. The stars -- blots, in Spitzer's view -- are seven-pointed beacons of light in the MIRI test.
Webb's next steps will focus on taking images of its science targets, known as early release observations. These will not only be the first images of Webb science targets, but they will be the first images processed into full color. (Webb sees the cosmos in the infrared and near-infrared wavelengths, but the images will be translated into visible light.) Klaus Pontoppidan, a Webb project scientist at the Space Telescope Science Institute, said in the briefing that the chief differences between the most recent images and the ones to come are that the former were taken to test the telescope's ability to see clearly, whereas the latter will test the telescope's ability to image science targets. Pontoppidan wouldn't elaborate on what Webb team will capture in the early release observations -- the targets are a "surprise," he said.
Re:good to know (Score:5, Insightful)
Nice to see that NASA mostly has its priorities straight
The decision to build and launch JWST was made 25 years ago.
JWST has little to do with the priorities or politics of the people running NASA today.
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Because that's what you're claiming about literally the entire universe beyond Earth: That sending people out there would somehow produce less good understanding than sitting on our asses looking through instruments from inside our infinitesimal little comfort zone.
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It's weird that so many people think probe science and human spaceflight are at odds. Do you feel like you have a lesser understanding of the place you live than someone who lives far away and studies it by looking at photos of it? Because that's what you're claiming about literally the entire universe beyond Earth: That sending people out there would somehow produce less good understanding than sitting on our asses looking through instruments from inside our infinitesimal little comfort zone.
Are you serious? Nobody is saying that sending a human to observe something/somewhere 'in person' gives lower quality info than images captured from afar. The point is, sending humans is orders of magnitude more expensive, and in most cases not even possible with current technology. You're suggesting we somehow send a human to the crab nebula rather than use a telescope? Any plans on how we do that? You think sending a human to mars is going to further our understanding of the universe more than buildin
Re:good to know (Score:4, Insightful)
Numbers: Singular vs. Plural. (Score:5, Insightful)
Sending humans to Mars is going to further our understanding of Mars a hell of a lot more than sending a rover will.
(emphasis mine).
I think you're overlooking a specific detail: the grammatical number you used in this sentence.
Sending a single human to Mars requires a vast amount of resources:
- some food/air supply
- extra equipment to ensure growing additional food / producing more air further into the mission
- some space (living quarters) for the human to live in (and rest) during the travel (human aren't very well suited to being flatpaked for shipment).
- extra equipment to build a settlement for the human to live in (and rest) during the mission and/or having the travelling vessel large enough to serve a living settlement itself.
- a ton of extra equipment to carry the human back to earth after the end of the mission, including whatever would be needed to synthetise the necessary fuel (and keep in mind that the gravity well you'd need to escape at the beginning of the return journey is going to be a bit less trivial than the moons. with extra drag on top)
In short even for one (1) single human, you would need to ship quite some hardware.
For the same amount of mass you could ship a large quantity of robots.
Also, we humans tend to no appreciate losing other members of our species - whereas losing robots would cost us only money.
Thus shipping humans would require even more stringent specs for the shipping.
Basically, as expensive it might be, it's still much cheaper and easier to send a shit ton of robots, than to send a couple of humans to Mars.
So yes, a single human on Mars' surface could further our understanding more than a single robots.
Except it's still cheaper, simpler and safer to send a whole army of robots, which collectively would still further our understanding a lot.
We're not going to space today.
Not before we've reached the point where we're hesitating to between
- "send an extra 200 robots to Mars to complement the 10'000 already present there"
or
- "send only 50 of them, and use the remaining resources to send a crew of 3 humans, and divert some work of the robots already on ground there+some of those shipped to prepare the environment so the crew survives and prepare everything necessary so they can be safely flown back".
Given the recent advances in space flight and current proposals to explore the moon and eventually Mars, I think it is rather premature to dismiss manned space exploration as "too expensive to bother with".
Tsiolkovsky rocket equation is a bitch.
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The moon is covered in resources.
The Apollo missions were grandstanding. The current set of moon ambitions are designed to go and do useful things.
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Sending humans to Mars is going to further our understanding of Mars a hell of a lot more than sending a rover will.
(emphasis mine).
I think you're overlooking a specific detail: the grammatical number you used in this sentence.
Sending a single human to Mars requires a vast amount of resources: -
So?
This always comes up, where someone thinks it's just too hard. So what? It's also hard to send robots - so why bother.
Ol Muskie for as much as I disdain his more rabid fans, is on to something. Inspiration. The idea of people doing something. I don't even care for his plan, but the inspiration is telling us something.
If we aren't planning to eventually go to Mars, there is precious little point in sending anything there. I'm into the science of it, but if we don't learn anything - why would it
Justifications (Score:2)
This always comes up, where someone thinks it's just too hard. So what? It's also hard to send robots - so why bother.
It's not too hard. It's technically doable.
It's merely more expensive, more complex and riskier to send human.
Which simply means it will be hard to justify sending humans for science, when sending robots gives more bang for your bucks.
So the later would be easier to justify, even more so when the budget is provided by the government and needs to be balanced against other government spending.
Though I'm not saying we will never go to space.
We will probably not go space "For Science!", because you can do dispr
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This always comes up, where someone thinks it's just too hard. So what? It's also hard to send robots - so why bother.
It's not too hard. It's technically doable. It's merely more expensive, more complex and riskier to send human.
Of that, there is not doubt. I'll bet this has been an age old story, between the adventurers, and the risk averse.
A lot of people are risk averse, especially in today's safety culture world where any risk is considered bad. There is a subset of humanity that has a lot of wanderlust. That is not particularly risk averse. And throughout history, those are the people who have made history.
Not that I'm going to make history, but I've never shied away from rewarding activities because of risk. I played
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Until AI becomes fully human, people will be the only solution to the latency problem in space exploration. If and when AI does become fully human, would we then still consider it a separate form of intelligence>
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Re: good to know (Score:5, Insightful)
Re: good to know (Score:5, Interesting)
Obviously, there hasn't been a full mass extinction event for humans/apes since our ancestors climbed down from the trees.
Also, while climate change is an existential risk, even the most gruesome projections depict an Earth that's a veritable paradise compared to Mars.
So the only known thing a second planet hedges against to some extent, is a total civilization collapse due to nuclear war, or some future version of the LHC making a mini black hole that can suck in an entire planet, or some nano/bio agent.
But with two, or a few more eggs in the basket, and the likely fractioning of people on the other planets, as well as the interplanetary spread of nuclear, nano- and biotechnology, the risks are only lessened somewhat, rather than eliminated.
Still a good thing.
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human space travel goals to further politicians' goals.
If that were the case then private enterprise would have no interest in it.
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human space travel goals to further politicians' goals.
If that were the case then private enterprise would have no interest in it.
Private enterprise is happy to receive those subsidies though.
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rivate enterprise is happy to receive those subsidies though.
Contracts gained by undercutting NASA's traditional suppliers are not "subsidies."
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If that were the case then private enterprise would have no interest in it.
Cut off government dollars from privately owned spaceflight, and see how interested it is.
Not that I suggest such a thing- the system is working as designed as is. I'm just pointing out that your claim is ridiculous.
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Nice to see that NASA mostly has its priorities straight and employs space technology to further our knowledge of the universe, rather than pursue vain human space travel goals to further politicians' goals.
Apparently needs to be requoted against censor trolls, but I really don't see what they were upset by in the comment. Vacuous Subject isn't a big problem?
A fantastic achievement (Score:2)
But there's just a tiny part of me that wishes it was also a full insted of partial optical band wavelength telescope too so it could fully replace hubble. Obviously they had their engineering reasons not to but I wonder - just how hard would it have been to add that extra 0.2um so it could see into the blue instead of stopping at yellow given it has a huge bandwidth up to 28um.
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Unfortunately it has a limited life-span, it can't replace Hubble, so it is focused on what it can do better than any other telescope, infrared.
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Generations have been raised with our wonder for the cosmos firmly planted in the images produced by Hubble.
Re:A fantastic achievement (Score:5, Informative)
Hubble is being replaced by Nancy Grace Roman. It's one of those Hubble-duplicate mirrors the spooks gave NASA. It will have about the same resolution as Hubble but cover a much larger field of view, and has all new modern instruments.
If you're looking for just-Hubble-but-bigger then you've got two main problems: 1) Hubble has done a lot of the interesting science in that area and 2) adaptive optics cancel much of the advantages space telescopes have in the visible spectrum. There's not a lot of point in making a bigger-than-Hubble space telescope at the moment because we can (and are) making holy-shit-bigger-than-Hubble ground telescopes.
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There's not a lot of point in making a bigger-than-Hubble space telescope at the moment because we can (and are) making holy-shit-bigger-than-Hubble ground telescopes.
We are- and there are huge benefits they can provide via adaptive optics and their ridiculous aperture sizes, however, there is as-yet no ground telescope that can match hubble imagery.
You can fix turbulent refraction in the atmosphere. You can't fix its refractive index, as a whole, though.
Both better ground telescopes and better space telescopes are both worth pursuing, with different pros and cons for both.
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In the visible? The current crop of 10 m telescopes more than compete with Hubble, and the thirty metre ones coming will blow it away.
Space telescopes are definitely worth pursuing, but pursuing for their unique advantages: wavelengths that don't get to the ground (like JWST), the Roman telescope's coronograph, and hopefully in the future star shades, space-based ultra long baseline interferometry, and eventually enormous telescopes assembled in space that could never support their own weight on a planet.
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30m scopes will be even better, but again, there are limits to where the adaptive optics can be utilized in the sky.
And remember- we're comparing them against a 2.4m reflector in orbit.
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Sure, but science money unfortunately isn't infinite. If you want, say, a 5 m Hubble you need to trade somewhere between sixteen and forty (probably on the high end) Gran Telescopio Canariases for it.
I think they made a good choice with the Roman telescope. It's sixteen Telescopio Canariases, but it can do most or all of what Hubble did with 100 times the field of view so you can get some solid statistics, and also directly image exoplanets.
Now, if people would skip buying Hallowe'en costumes for their pets
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However, we will reach a point where it becomes unreasonable to make larger reflectors on the ground (even with newer segmented deformable mirrors), and still reasonable to send much smaller segmented mirrors into orbit.
Synthetic aperture is awesome, but comes with a necessary reduction in sensitivity, so we're really stuck comparing monolithic (segmented or otherwise) reflectors.
A 10m scope in orbit will outperform a 30m scope on the
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Hopefully by the time it becomes impractical to build bigger telescopes on the ground we just start building them in orbit. Imagine an orbital casting and polishing factory turning out 100 m mirror segments.
Re:A fantastic achievement (Score:5, Interesting)
JWST must be in space because earth's atmosphere is utterly opaque to nearly all the bands it observes in (red to warm thermal IR).
Moreover, absent a spectacular jump in diffraction limit resolution (think a spaceborne optical interferometer using Keck-size mirrors in a kilometer-size triangle), I think it is felt that the two major targets of scientific observation - protoplanetary systems and the early universe - both require infrared observation. Protoplanetary disks because shortwave radiation is completely scattered by dust, so that we can only image embedded objects inside dusty disks using IR all the way out to mm wave radiation. The early universe because metric expansion has turned everything far out there red, or IR, or further.
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Sure, I accept all that. I'm just wondering how hard it would have been to extend its bandwidth by another 0.2um given how wide it is already. I'm not suggesting sacrifice some of its its IR ability.
Re:A fantastic achievement (Score:4, Interesting)
Pretty hard. Each NIRCam module (there are two) is basically two cameras glued together, observing in two bands, 0.6-2.3 um and 2.4-5.0 um. To get something approximating a colour image you'd have to add two more, in the green and blue. But the big problem is that gold optical coatings have reflectivity that drops off pretty precipitously around 0.5-0.5 um:
https://www.thorlabs.com/image... [thorlabs.com]
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Astronomical cameras usually don't create color images by taking exposures with 3 sensors simultaneously. They have one sensor, and a filter wheel. Each of NIRCam's sensors have 12 filters available, some wideband (comparable to red, green, blue), some narrowband to see specific emissions. So NIRcam can create color images already.
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The OP was talking about visual spectrum so I meant "colour image" as in visible spectrum, three bands close to what our eyes see. NIRCam is missing green and blue. I should have been more specific.
I think NIRcam actually can take images simultaneously (but just two of the same target?) because it has dichroic beam splitters.
And yes, there's a pretty good chance none of the famous Hubble images that come to anyone's mind are actually red, green and blue channels anyway.
Re:A fantastic achievement (Score:4, Informative)
Light pollution (thanks to Musk)? I'd call that a big reason. Also, adaptive optics on the ground will do a fair bit, but Earth's atmosphere is increasingly humid and polluted. AO will counter humidity some, but you can't correct for pollution. Since this will vary with angle (since the amount of atmosphere you go through increases), tracking and AO gets complicated. Then there's the geopolitics, as shown in Hawaii. You can't Keep It Simple and you can't be sure of keeping it at all. And then there's the sun. It means you are limited in time when you can view.
The atmosphere isn't merely problematic due to distortions, though. If you want to study absorption lines in the atmosphere of another planet, it's quite a lot tougher if our own atmosphere absorbs visible light at those same frequencies.
Telescopes in space aren't on owned property, can be rotated to any angle without having to constantly compensate for atmosphere, humidity or pollution (all of which will vary by time and by the angle you're looking through the atmosphere at), and can be used all of the time. Rotation plus constant use is also very handy for deep field work.
That's a lot of benefit.
You can also use AO in space to counter limitations in the mirrors. Having AO to fix fabrication issues and distortions introduced to due launch vibrations would certainly help.
Re:A fantastic achievement (Score:5, Interesting)
On the other hand thanks to Musk you could in the near future launch an ~8m primary mirror space telescope and not have the artefacts from it being separate panels.
Given the JWT took 25 years to get into space NASA and associated agencies should start planing for such a beast now.
You could even think bigger and do an even larger folding mirror telescope in JWT style.
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But why? Before you jump to a solution consider the problem you're trying to solve.
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Because a bigger telescope is better, and as the previous poster made clear some observations are difficult to do on the ground. Nobody suggests that you need to work out what problem you want to solve by designing a faster computer. It is taken as a given that a faster computer is useful. In the same manner a larger telescope is useful.
There are some plans for large space telescopes but they are being designed around a standard 5m faring. That's banana nuts with SpaceX's Starship going to be ready long (ev
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You seem to know your stuff.
Can you explain how the octagonal star rays in the high resolution picture come to be? If that is an effect of the telescope's optics, a physical property of the star or light itself, or some other reason?
There's also a fractal aspect to them.
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Hexagonal. It's due to JWST being composed of hexagonal mirror sections. The four long diffraction spikes are from the secondary mirror support trusses.
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Probably, at least for some of them. You could do it yourself too. Deconvolution is pretty simple but fun to play with.
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I'm counting 8 rays on those stars...
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If you zoom in on one of the bright stars you can see that the central bright spot looks like a slightly blurry hexagon, with each face having a sort of fleur de lis or club (from cards) shape coming out of it. Then there are four big spikes in each vertical and horizontal direction (the horizontal ones line up with the clubs and the vertical ones fall in between. In between the four big spikes are arrays of fainter spikes.
I misspoke, JWST only has three support trusses for the secondary mirror. The extra
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Geometric optics suggests that a (correctly focused) telescope would focus an incoming plane wave (parallel wavefront, light from an infinitely distant source - a star) to a point. Quantum mechanics tells us that this isn't possible, and instead the best-focused image that can be generated from circular optics is called the Airy disk. It looks like a central big Gaussian bump with smaller ripples surrounding it, and the diffraction limit is defined in
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Holy crap, I have to read that a few more times to understand it. Thanks for the effort. 8-)
You also mention hexagonal, but I'm counting 8 rays on those stars.
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Yes. 6 large spikes from the mirror edges, 2 smaller spikes from the supports of the secondary mirror: the struts cause 4 spikes, 2 of which are lined up with the 6 large spikes.
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Interferometry offers excellent angular resolution per dollar, but it's also subject to rather poor sensitivity. You can math away the missing photons, but you math away the information they contained as well. Interferometry is not a replacement for standard aperture observation. It's another tool.
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I think the main point was to solve the problem of how to receive infra-red with adequate sensitivity to see the most distant objects, that have the most red-shifted spectra. There is nothing particularly magic about the narrow region of the electromagnetic spectrum that we can perceive with our eyes. My father spent his life observing radio sources in outer space, using terrestrial parabolic dishes. There is a lot of interesting stuff out there, that you won't see with a conventional telescope.
Re:A fantastic achievement (Score:5, Informative)
As the Universe is expanding, far away stars seem "redder" than closer stars.
As such, while JWST is partially "blind" for close stars, it can see the "red-shifted" and "infrared shifted" radiation generated.
Adding another sensor would make the alignment of mirrors even more complex than it is now, and the existing sensors were proven valuable enough not to be replaced.
Also, there is no value in putting an optical telescope in a Lagrange point. A new Hubble in Earth orbit would have been a small fraction of the cost.
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Interesting, what is the point of putting the JWT at a Lagrange point?
Re:A fantastic achievement (Score:4, Informative)
Interesting, what is the point of putting the JWT at a Lagrange point?
It can orbit the Lagrange point far enough out that it's never shadowed by the sun or moon, and with the Earth and Moon a good distance away. This means that it sees very little thermal variation and the small amount that does come from the earth can be shielded with a fixed shield.
Thermal expansion etc would play hell with alignment and they need to keep the IR sensor very very cold.
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The "solar" side of JWST reaches around up to 20 degrees Celsius (some 300 Kelvin, or - lets call it 70 Fahrenheit.
The "normal" infrared sensors should work at around 50 Kelvin (lets call it -220 Celsius). You can get there by keeping it in the shade of the multiple layer, tennis-court sized parasol.
The "cold" "deep infrared" sensor must be cooled down even more, so it has a refrigeration system.
Now, the issue with these is that - basically - once they "look" into the Sun, they're burnt.
So, JWST must stay "
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But there's just a tiny part of me that wishes it was also a full insted of partial optical band wavelength telescope too so it could fully replace hubble.
The most fantastic images released by the Hubble are actually false colour images, such as this one of one of the Pillars of Creation in the Eagle Nebula https://esahubble.org/images/o... [esahubble.org] The image is actually made up of largely infra-red response.
Space is actually incredibly boring in the human visible band.
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Space is actually incredibly boring in the human visible band.
In spite of your first paragraph being entirely correct- this is not.
I've done real-color space imagery for a long time (as soon as I could afford the hardware, really). Obviously, I don't have the Hubble's sensitivity, but I do have good tracking hardware and software, and space is still quite amazing in the human visible band.
The pillars of creation, while not as fabulously colorful as that, are still wildly impressive.
Re:A fantastic achievement (Score:4, Informative)
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I could see star-shaped optical artefacts. (Score:2)
Though the Webb telescope images in the article did show up many more sources than previous telescopes, I could not help noticing that bright sources produced arms of light, with four-fold symmetry. Is this something that you just can't avoid with an optical system? Optics is not my field of expertise, so I am just asking, in case somebody knows the answer.
The fact that we have an idea of a star shape, as observed by the naked eye, or magnified by a telescope, indicates that this kind of optical artefact is
Re:I could see star-shaped optical artefacts. (Score:5, Informative)
Those lines are called diffraction spikes. They are caused by the edges of the mirror segments, and by the 3 supports for the secondary mirror. Light diffracts on each edge.
They are hard to avoid. Round mirrors won't cause diffraction spikes, their diffraction shows up as a diffuse disk around the star.
There are telescope designs with an off-axis secondary, but those tend to introduce distortion.
The diffraction spikes are worst for very bright objects, much fainter for dim objects, and basically not there for diffuse objects like galaxies.
Many of the alignment images are overexposed, and the light curve is logarithmic, to make the spikes as bright as possible, because there's information on how good the mirror alignment is in those spikes. Science images won't be overexposed or use this light curve.
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The mirror in your Dobsonian doesn't produce diffraction spikes. The hexagonal mirror segments in JWST do produce diffraction spikes.
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As I said, instead of spikes, the edge of a round mirror produces diffraction in the form of an airy disk. Any straight edge that light can reflect off will cause a spike.
Protip:
1. read.
2. digest.
3. reply.
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As I said, instead of spikes, the edge of a round mirror produces diffraction in the form of an airy disk. Any straight edge that light can reflect off will cause a spike.
Protip:
1. read.
2. digest.
3. reply.
Sounds like sour grapes from someone who has never known the glory of getting a "First Post!".
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There is a design for segmented mirrors without diffraction spikes. There are some disadvantages though in total reflective surface area versus effective diameter, and JWST was limited in total diameter (it was launched with parts of the main mirror folded).
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Those lines are called diffraction spikes. They are caused by the edges of the mirror segments, and by the 3 supports for the secondary mirror. Light diffracts on each edge.
So basically the same as the way my cataracts cause me to see headlights and street lights with the same spikes around them.
Re:I could see star-shaped optical artefacts. (Score:5, Informative)
If you're interested in exactly what causes the shape of the diffraction spikes the other poster was talking about there's a good article which explains it in great detail.
Here's an image excerpt which explains the shape: https://bigthink.com/wp-conten... [bigthink.com]
And here the full article: https://bigthink.com/starts-wi... [bigthink.com]
The Hubble also has diffraction spikes which are the result of only the spider holding the secondary mirror: https://en.wikipedia.org/wiki/... [wikipedia.org] as opposed to the JWST which is the result of both the shape and layout of the mirrors as well as the spider.
This isn't limited to space telescopes either. E.g. a Newtonian telescope where the secondary mirror is held in place by a spider produces diffraction spikes as well: https://www.astrobin.com/7twta... [astrobin.com]
Those same diffraction spikes are absent from classic refractor telescopes: https://www.astrobin.com/1gzcf... [astrobin.com]
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You've basically got a choice between diffraction spikes, chromatic aberration and witchcraft mirror making.
Refractive telescopes, where the light goes through lenses, don't need any support in the light path, but refraction is wavelength dependent so you get chromatic aberration. There are also problems with focal length and various other things.
Large mirrors are much easier to make and you don't have chromatic aberration, but you need some way to support a secondary mirror in front of the primary. Those s
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The diffraction spikes really only show up when you're looking at something really bright.
I would have thought that the problem would be trying to observe a dim object at a small angular displacement from a bright object. The diffraction spikes from the bright object "splurge" over the stuff you are trying to observe. From what other people have posted on this subject, the artefacts are not due to imperfections in the construction of the telescope, but would occur in some form in a "perfect" instrument of a particular size.
The problem appears to be an instrument being dazzled by strong sources i
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That could be a problem, but if you wanted to image something close to a bright object you could rotate your telescope to put the object you're interested in between spikes. The JWST also has the hexagonal diffraction artifacts from the mirror segments, which would be harder to move out of the way, but that really only limits a few of the observations you can make.
You always have diffraction, you just get to choose what form it takes. A good telescope is "diffraction limited" meaning that its resolution is
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You've basically got a choice between diffraction spikes, chromatic aberration and witchcraft mirror making.
You could keep secondary mirror in place using magnets. Which could go as "witchcraft".
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Permanent magnets are definitely witchcraft, but you can't actually hold something in place with a static magnetic field (there's a proof and everything). So you're probably use electromagnets, which are just plain old special relativity.
Updated list:
diffraction spikes, chromatic aberration, witchcraft, or special relativity.
Error in summary (Score:5, Informative)
JWST does not "sit at L2", it is in a 300,000 x 800,000 km orbit around L2. This wide orbit ensures that the telescope is never shadowed by Earth or the Moon.
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They have to do a small trajectory correction maneuver every 2-3 weeks. This orbit is unstable, so without fuel, a spacecraft would start drifting away from the L2 point.
This type of orbit is called a halo orbit, IIRC.
Re: Error in summary (Score:2)
Here are more details about the JWST L2 orbit:
https://jwst-docs.stsci.edu/jw... [stsci.edu]
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L2 is unstable in "close" - "far" localization, but is stable in the other two axes. It stays "closer" to Earth than L2, and drifts "close" to Earth. The boosts send it back in the "almost L2 but on Earth side" position.
If it goes "past" L2, all is lost - it can only boost on the face without the telescope, and it can't turn towards Sun for reasons of burning the infrared detectors.
Gizmodo can't count (Score:1)
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There are EIGHT lights!
Six of them are from the hexagonal layout of the mirrors, the other two are from the horizontal part of JWST. So Gizmodo hires people who can't even count to ten?
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Oh good, it's not just me who sees eight.
Release them all (Score:1)
Re:Release them all (Score:4, Informative)
They will do just that, at the Mikulski Archive for Space Telescopes [stsci.edu]. There will be a period of exclusive access for most observations (so the astronomer whoe requested the observation gets the first chance to examine the data).
All of the alignment and calibration images (more than 50k) will be released at the end of the commissioning process.
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They don't want to show the Martians mooning the camera?
Re:Release them all (Score:4, Interesting)
NASA does that eventually. It just takes time as the underlying data can be huge. These PR friendly images are also heavily processed. MBs of data or a photo: Which do you think is easier to put in a press release?
Incidentally, I was talking to a moon conspiracist and one of their claims is that NASA has never released the moon photos that the astronauts took on the surface. The NASA photos were too perfect and that "real" photos would contain mistakes: lighting issues, framing problems, etc. I was able to pull up the NASA archive online and show him all the photos. Some of them were obvious mistakes like taking a photo of complete darkness. Bear in mind these were the days of film and the astronauts had to be careful with each photo as they couldn't run to the store to get more film. Other photos had bad framing and bad lighting. When NASA released these photos in PR releases, they do basic editing like cropping and light balancing.
Increased resolution (Score:2)
The middle section of the article has a before/after image comparison. It's roughly the same as someone who puts on an everyday piece of eyewear before driving, maybe 2 diopters? Is it the approx. improvement in resolution? Somehow I assumed it'd be like getting the right side image from just a small speck on the left side image. There's also a lot more glare than on the left, which I guess could be computationally eliminated
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What are you calling "glare"? The bright effect of the stars? That's just the general nature of optics. Changes in resolution do not affect the bright objects from blooming. Both images are diffraction limited at their respective wavelengths. But quite critically the JWST is diffraction limited to 2um while the Spitzer is diffraction limited only to 5.4um. What that means is that JWST can still take tac sharp images at 2um while the Spitzer produces images that look pretty bad at those wavelengths (much wor
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For the short-wavelength channel, NIRCam uses 4 detectors that are 2048x2048 each. The long-wavelength channel has 1 detector.