The James Webb Space Telescope

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The James Webb Space Telescope (JWST) is scheduled to launch no earlier than December 24, following a two-day delay, with a critical launch window extending to January 6 due to gravitational concerns. Enthusiasm is high among the community, with many eagerly anticipating the scientific data it will provide, despite concerns over the lengthy wait and significant costs associated with the project. Initial observing time has been allocated for various proposals, including a major project called Cosmos Web, which aims to capture detailed images of the early universe. The mission's success is seen as a gamble, with many previous missions sacrificed for JWST funding, raising questions about the return on investment. As the launch approaches, excitement and nervousness are palpable, with many setting alarms to witness the event live.
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  • #352
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  • #353
@Devin-M are we supposed to guess what those are?
 
  • #354
phyzguy said:
Astronomy has the interesting practice that nothing ever gets re-defined. Hipparchus defined the magnitude scale almost 3000 more than 2000 years ago, and called the brightest stars 1st magnitude, the next brightest 2nd magnitude, and so on. So we are stuck with a magnitude scale that runs backwards - where brighter stars have a smaller magnitude than dimmer stars.

Population I and Population II were defined before anyone knew why they were different and that Population II came before Population I.

The numbering makes sense to me. You know you can see the brightest stars, and who the heck knows how many classifications you're going to want for the stars you can't see yet.
 
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  • #355
phinds said:
@Devin-M are we supposed to guess what those are?
test.jpg
Here's what it would look like through a 2000mm telescope in Stellarium:
Screen Shot 2022-07-29 at 10.38.32 AM.png

RA 11h06m18.79s Dec -77º22'50.9"

James Webb NIRCam:
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100% Crop:
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  • #356
Office_Shredder said:
The numbering makes sense to me. You know you can see the brightest stars, and who the heck knows how many classifications you're going to want for the stars you can't see yet.
When it was just a numbering classification, it made perfect sense, which is why Hipparchus defined it that way. But later, when quantitative measurements of brightness arrived, we turned it into a quantitative magnitude scale for measuring brightness. After doing that, we really would rather have a brighter object have a larger magnitude. But that would mean re-defining the scale. So today, the faintest objects we can see with our eyes are m=6.0, the faintest objects seen in large telescopes are about m=30.0 and the sun is m=-26.
 
  • #357
RA 01:07:47.200 DEC -17:30:25.00
JWST NIRCam Bi-Color, F150W & F200W Filters, 2319s exp per filter
Processed w/ SiriL, Adobe Photoshop & Lightroom
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  • #358
RA 2:17:46 DEC -05:16:15
JWST NIRCam 7-29-22 12:04
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  • #359
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  • #360
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  • #361
1 Sensor:
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8 Sensor Mosaic:
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  • #362
NGC 3324 MIRI Composite - Filters: 770W (Blue), 1130W (Green), 1280W (Red)

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100% Crop:
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100% Crop:
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  • #363
Messier 92 (Globular Cluster):
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1 Sensor:
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  • #364
IC 5332 Galaxy
MIRI Instrument, Filters: F1130W & F2100W
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  • #365
Hubble verses Webb- Earendel

1659612486192.png
 
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  • #366
I'm confused. If those are pics of the same area, how is it possible that the orientation / arrangement of the galaxies is so different?
1659613760985.png
 
  • #367
phinds said:
I'm confused. If those are pics of the same area, how is it possible that the orientation / arrangement of the galaxies is so different?
One picture is rotated in respect to the other.
 
  • #368
Motore said:
One picture is rotated in respect to the other.
AH HA! I was looking for 90-degree flips/mirrors/whatever. Not very bright this morning. Thanks.
 
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  • #369
phinds said:
AH HA! I was looking for 90-degree flips/mirrors/whatever. Not very bright this morning. Thanks.
About 33deg

1659614735681.png
 
  • #370
pinball1970 said:
About 33deg
I'm up way too early this morning (long story) and I was only able to think in 90 degree increments. :oldlaugh:
 
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  • #372
NGC 1365:
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  • #373
This is the other post I have been looking for but I cannot find a full article or paper on it

https://www.newscientist.com/articl...otted-by-jwst-may-be-closer-than-they-appear/

This link mentions a calibration update but I am not subscribed so cannot read the rest.

The article I read/saw that I did not have time to post frustratingly, mentioned JWST ability to detect IR much better than any telescope before it. Therefore Galaxies "appear" to be further away than they actually are and the error could be as much as 20%.

This confused me, I though the whole point was Webb was designed for that very purpose so what did they expect?

Is that not an intensity rather than wavelength issue? Because the mirror is huge? collecting more photons?

Also, is it not possible to distinguish IR from a shorter wavelength that is red shifted to IR? What about Blue, red shifted to IR? UV?

Seems I don't get red shift at all (I am on it)

Like I said I can only apologize for the vagueness I am hoping that link will have the article with the link to an actual paper.
 
  • #374
pinball1970 said:
The article I read/saw that I did not have time to post frustratingly, mentioned JWST ability to detect IR much better than any telescope before it. Therefore Galaxies "appear" to be further away than they actually are and the error could be as much as 20%.
That doesn't seem to make sense, but it's hard to judge without context. Maybe they just discuss how certain parameters are still not very well known, but that should be a symmetric uncertainty.
pinball1970 said:
Also, is it not possible to distinguish IR from a shorter wavelength that is red shifted to IR? What about Blue, red shifted to IR? UV?
It's only possible if you can find spectroscopic lines or use other spectroscopic features (like the Lyman break). Taken on its own a UV photon redshifted by a factor 15 to 3 micrometers and a visible light photon redshifted by a factor 5 to 3 micrometers are identical.
 
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  • #375
mfb said:
That doesn't seem to make sense, but it's hard to judge without context. Maybe they just discuss how certain parameters are still not very well known, but that should be a symmetric uncertainty.It's only possible if you can find spectroscopic lines or use other spectroscopic features (like the Lyman break). Taken on its own a UV photon redshifted by a factor 15 to 3 micrometers and a visible light photon redshifted by a factor 5 to 3 micrometers are identical.
Ok That makes sense thanks. I think I have come across that before

If I find that article I will post it and get your/pf view.
 
  • #376
pinball1970 said:
Ok That makes sense thanks. I think I have come across that before

If I find that article I will post it and get your/pf view.
I have a subscription and the article contains the following relevant sentence:
NIRCam (one of the main cameras on the telescope) was overperforming in its reddest wavelengths.
This suggests that the problem affected calculations that compared the relative brightness at different wavelengths.
 
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  • #377
pinball1970 said:
Therefore Galaxies "appear" to be further away than they actually are and the error could be as much as 20%.
The shift only tells you the recession speed and, although the shift of the (faint) spectral lines can only be measured to a certain accuracy, the distance that's calculated from that red shift depends on the Hubble constant being a constant. Another quantity that can be measured is the brightness of the observed objects and that can be affected by (unknown) quantities of dust etc. Will they actually know the sort of spectral tilt out towards the IR? I imagine that could affect their distance estimation. But someone will sort it out, I'm sure, with the appropriate frigg factor.
 
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  • #378
Jonathan Scott said:
This suggests that the problem affected calculations that compared the relative brightness at different wavelengths.
Would fit to the Lyman break, which is a drop in intensity at a specific wavelength. A miscalibration of the relative brightness shifts the fitted wavelength.

There is a twitter bot announcing the current JWST observation target with a reference to the science proposal: https://twitter.com/jwstobservation. Example:
I am now observing P330E using NIRCam Engineering Imaging for 4 hours and 20 minutes. Keywords: G dwarfs. Proposal: https://stsci.edu/jwst/phase2-public/1538.pdf 55:1
 
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  • #379
Finally found the link that specifically mentions this 20%

https://www.vice.com/en/article/5d3...ames-webb-may-not-be-so-distant-due-to-errors

The pre print

https://arxiv.org/abs/2207.11217

Adams

“When we get spectroscopy, I have little doubt that some of these galaxies we thought were very high redshifts will turn out not to be,” Adams concluded. “But with that solid answer to hand, we can begin the process of figuring out why and refining our techniques. After all, that's what science is about!”
 
  • #380
pinball1970 said:
When we get spectroscopy, I have little doubt that some of these galaxies we thought were very high redshifts will turn out not to be,”
That statement seems to show some careless publicity of their results. How ever could they be sure about the red shift if they haven't actually measured it? A bit egg on face iyam.
 
  • #382
100 AU away from its star at a distance of 400 AU light years.

A planet orbiting one of the stars of Alpha Centauri at 1 AU would have a similar apparent distance and this looks well-separated from the parent star, so in principle a couple of habitable planets could get direct images and spectra from JWST.
 
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  • #383
mfb said:
100 AU away from its star at a distance of 400 AU.
I think you mean 400 light years.
 
  • #384
A nice side by side comparison of Hubble and JWST. ORION NEBULA
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  • #385
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  • #386
I had a quick search on Webb for updates on that issue with MIRI

I did not find anything.

This image was on the site though, “Webb Reveals Shells of Dust Surrounding Brilliant Binary Star System.”

1666253408455.png


What is this top right? It looks very symmetrical in shape and colour, just an optical effect from the telescope like diffraction spikes?

1666253518991.png
 
  • #387
pinball1970 said:
just an optical effect from the telescope like diffraction spikes?
You may be right but if the effect is being introduced locally (to the telescope) then what could be special about the light from the star? It doesn't occur for other stars.
The effect seems to be a rare one.
Those regular fringes extend over millions of km, if we assume they're actually around the star. There's nothing that uniform around a star so if it were 'waves of ejecta', due to regular explosions, the spacing would change with distance unless the speeds are colossal and the star's gravity is having negligible effect. A series of images, over a long period, could reveal motion but wouldn't that require a very long timescale?
 
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  • #388
pinball1970 said:
just an optical effect from the telescope like diffraction spikes?
Maybe dust from the main star being imaged? The other stars may be in front of the dust.
 
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  • #389
Borg said:
Maybe dust from the main star being imaged? The other stars may be in front of the dust.
Possibly but no apparent colour fringes and the star is not monochromatic.
Weird.
 
  • #391
Side side with Hubble on the left from 2014
I turned on all the lights off in the office so I could see this in all its glory.
Wow.

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  • #392
sophiecentaur said:
Weird.
Perhaps I am reading tea leaves. The hexagonal pattern is obviously from the optics (likely the mirror shape) but to my eye the green shape is rotated 30o relatve to the red one. I having trouble figuring a plausability argument for that, either diffraction or refraction. One also should be cognizant that these are false colors.
 
  • #393
But why aren’t all (bright) star images like it?
 
  • #394
sophiecentaur said:
But why aren’t all (bright) star images like it?
My best guess (I just thought of it) is that it looks like the internal "camera" reflection from either the bright object in field or perhaps one just out of field off axis. I don't know enough about Webb optics to be any more definitive
 
  • #395
hutchphd said:
My best guess (I just thought of it) is that it looks like the internal "camera" reflection from either the bright object in field or perhaps one just out of field off axis. I don't know enough about Webb optics to be any more definitive
I tried blowing up some of the other objects but they all were too blurred.
 
  • #396
Is there a NASA source to get such images with full resolution?
 
  • #397
pinball1970 said:
I tried blowing up some of the other objects
Did you borrow Peter's blaster again? I thought we already had "the talk" about that... :wink:

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https://www.deviantart.com/nocturnbros/art/Marvin-the-Martian-invades-DEATH-BATTLE-683673659
 
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  • #398
anorlunda said:
Is there a NASA source to get such images with full resolution?
The image is from the NASA site. I have been looking at other images and cannot see anything like this.
Dust has been mentioned, if it is fairly evenly distributed then could the rings which look almost concentric cause that effect via some sort diffraction?
 

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