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JWST vs Spitzer in near infrared is a striking difference: https://twitter.com/gbrammer/status/1504369779540480002 https://twitter.com/gbrammer/status/150436977

JWST vs Spitzer in near infrared is a striking difference: https://twitter.com/gbrammer/status/1504369779540480002 https://twitter.com/gbrammer/status/1504369779540480002

floxy 5y ago
That's a cool photo. Is there a similar comparison of that photo from the JWST to one done in visible light?
- sbierwagen 5y ago
  Not really. Ten minutes of googling didn't find anybody pointing a high resolution instrument at HD 84406, just sky surveys. From this comment https://news.ycombinator.com/item?id=30093849 https://news.ycombinator.com/item?id=30093849 here's one square degree (3600 square arcminutes) of sky around the star: https://bsrender.io/sample_renderings/hd84406-1deg-m18-ax1000-ao127-2k.png https://bsrender.io/sample_renderings/hd84406-1deg-m18-ax100... If the published calibration image is a single NIRcam exposure, then it's a 2.2x2.2 arcminute square around the central star, or, at the scale of the Gaia photo, a 33x33 pixel box. The Airy disk pretty much takes up the whole thing at that scale. You can also take a look via CDS portal: http://cdsportal.u-strasbg.fr/?target=HD%20%2084406 http://cdsportal.u-strasbg.fr/?target=HD%20%2084406 Various sky surveys also show little detail at 2.2 arcmin.
  - sbierwagen 5y ago
    Math error: should be 73x73 pixels. (2000 pixels divided by 60 to get pixels per arcminute, then multiplied by 2.2 to get total pixels)
jakear 5y ago
I think the real question is whether the images will generally look distinctly different from existing space telescope images. In the example you provide, the JWST image is only remarkable because the sampled area is too small for Spitzer to accurately resolve. If you were not comparing area to area but instead just trying to find an image that looked almost identical to JWST's, it would be much harder to spot the improvement. Think of looking at a mountain. It looks like a mountain. Then focus on a cliff of that mountain. It looks really quite similar to the mountain. Focus on a boulder on that cliff. Again, quite similar. A rock on that boulder. Similar. It's only when you reach the microscopic/atomic scale that the structure is revealed to be something totally different from what it was before and you learn it's not rocks all the way down. There's something different there, but it requires spanning a very large number of magnitudes to arrive at it. Now, we've seen some different things from existing telescopes. Galaxies, nebulas, etc. look absolutely nothing like stars as seen by the eye (a bit like how you're sure to happen by plants and animals while zooming into that mountain). But as the resolution increases I am not sure that we've had that next leap. The Hubble deep field image for instance looks basically the same as the Hubble ultra deep field. In short, will JWST reveal new structures so distinct from anything we've seen before that upon looking at an image it's immediately obvious that such an image could only have come from JWST, or will the images look like the plethora of existing telescope images, just at a different scale? I certainly hope for the former but my intuition is leaning more towards the latter. I'd absolutely love to be proven wrong here.
- MAGZine 5y ago
  Why not both? The JWST contains entirely different class of equipment, none of the likes has been included before. It also includes some of the largest equipment, huge mirrors that are capable of capturing huge quantities of light. Because of the frequency it is planning on looking at (enabled by how cold they're making the instruments), and because of the size of the mirrors (more light from dim sources), the JWST is going to be able to see waayyyy further, more dim, more old objects than any other telescope before. This is why the JWST is so exciting at all. It's going to tell us a LOT about the early history of the Universe. The JWST is not about putting the iPhone 13 in space when we already have an iPhone 12. It's more akin to putting an X-Ray camera on the iPhone. Actually, "that telescope but more," projects are few and far between these days: most agencies aren't interested in doing "the same but a little more,"--most projects optimize for where the biggest difference can be made in science. As an aside, you downplay the importance of angular resolution. If we're talking about visible light, having a space telescope take a picture of a galaxy in the visible spectra is obviously different and more useful than your phone/eye capture the "same" photons. Extra resolution is always enlighting because it provides us more information. Maybe that single point of light is actually not a single point of light, for example.
- rrrrrrrrrrrryan 5y ago
  Well, it'll be able to take direct photos of exoplanets and give us the data to analyze their atmospheres for signs of life. They photos won't look like much, but if any of the planets do end up having signs of life, that'll be far more thrilling than any pretty space photo could ever be.

JWST vs Spitzer in near infrared is a striking difference: https://twitter.com/gbrammer/status/1504369779540480002 https://twitter.com/gbrammer/status/1504369779540480002

floxy 5y ago

That's a cool photo. Is there a similar comparison of that photo from the JWST to one done in visible light?

sbierwagen 5y ago
Not really. Ten minutes of googling didn't find anybody pointing a high resolution instrument at HD 84406, just sky surveys. From this comment https://news.ycombinator.com/item?id=30093849 https://news.ycombinator.com/item?id=30093849 here's one square degree (3600 square arcminutes) of sky around the star: https://bsrender.io/sample_renderings/hd84406-1deg-m18-ax1000-ao127-2k.png https://bsrender.io/sample_renderings/hd84406-1deg-m18-ax100... If the published calibration image is a single NIRcam exposure, then it's a 2.2x2.2 arcminute square around the central star, or, at the scale of the Gaia photo, a 33x33 pixel box. The Airy disk pretty much takes up the whole thing at that scale. You can also take a look via CDS portal: http://cdsportal.u-strasbg.fr/?target=HD%20%2084406 http://cdsportal.u-strasbg.fr/?target=HD%20%2084406 Various sky surveys also show little detail at 2.2 arcmin.
- sbierwagen 5y ago
  Math error: should be 73x73 pixels. (2000 pixels divided by 60 to get pixels per arcminute, then multiplied by 2.2 to get total pixels)

jakear 5y ago

I think the real question is whether the images will generally look distinctly different from existing space telescope images. In the example you provide, the JWST image is only remarkable because the sampled area is too small for Spitzer to accurately resolve. If you were not comparing area to area but instead just trying to find an image that looked almost identical to JWST's, it would be much harder to spot the improvement. Think of looking at a mountain. It looks like a mountain. Then focus on a cliff of that mountain. It looks really quite similar to the mountain. Focus on a boulder on that cliff. Again, quite similar. A rock on that boulder. Similar. It's only when you reach the microscopic/atomic scale that the structure is revealed to be something totally different from what it was before and you learn it's not rocks all the way down. There's something different there, but it requires spanning a very large number of magnitudes to arrive at it. Now, we've seen some different things from existing telescopes. Galaxies, nebulas, etc. look absolutely nothing like stars as seen by the eye (a bit like how you're sure to happen by plants and animals while zooming into that mountain). But as the resolution increases I am not sure that we've had that next leap. The Hubble deep field image for instance looks basically the same as the Hubble ultra deep field. In short, will JWST reveal new structures so distinct from anything we've seen before that upon looking at an image it's immediately obvious that such an image could only have come from JWST, or will the images look like the plethora of existing telescope images, just at a different scale? I certainly hope for the former but my intuition is leaning more towards the latter. I'd absolutely love to be proven wrong here.

MAGZine 5y ago
Why not both? The JWST contains entirely different class of equipment, none of the likes has been included before. It also includes some of the largest equipment, huge mirrors that are capable of capturing huge quantities of light. Because of the frequency it is planning on looking at (enabled by how cold they're making the instruments), and because of the size of the mirrors (more light from dim sources), the JWST is going to be able to see waayyyy further, more dim, more old objects than any other telescope before. This is why the JWST is so exciting at all. It's going to tell us a LOT about the early history of the Universe. The JWST is not about putting the iPhone 13 in space when we already have an iPhone 12. It's more akin to putting an X-Ray camera on the iPhone. Actually, "that telescope but more," projects are few and far between these days: most agencies aren't interested in doing "the same but a little more,"--most projects optimize for where the biggest difference can be made in science. As an aside, you downplay the importance of angular resolution. If we're talking about visible light, having a space telescope take a picture of a galaxy in the visible spectra is obviously different and more useful than your phone/eye capture the "same" photons. Extra resolution is always enlighting because it provides us more information. Maybe that single point of light is actually not a single point of light, for example.
rrrrrrrrrrrryan 5y ago
Well, it'll be able to take direct photos of exoplanets and give us the data to analyze their atmospheres for signs of life. They photos won't look like much, but if any of the planets do end up having signs of life, that'll be far more thrilling than any pretty space photo could ever be.