The James Webb Space Telescope

[DennisN]

Two Weeks In, the Webb Space Telescope Is Reshaping Astronomy​

https://www.quantamagazine.org/two-...ce-telescope-is-reshaping-astronomy-20220725/

Stunning photos in that article!
The first one (of galaxy NGC 7496) is just incredibly beautiful!

 

[Devin-M]

 

[phinds]

@Devin-M are we supposed to guess what those are?

 

[Office_Shredder]

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.

 

[Devin-M]

@Devin-M are we supposed to guess what those are?

Here's what it would look like through a 2000mm telescope in Stellarium:

RA 11h06m18.79s Dec -77º22'50.9"

James Webb NIRCam:

100% Crop:

 

[phyzguy]

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.

 

[Devin-M]

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

100% Crop:

 

[Devin-M]

RA 2:17:46 DEC -05:16:15
JWST NIRCam 7-29-22 12:04

 

[Devin-M]

 

[Devin-M]

 

[Devin-M]

1 Sensor:

8 Sensor Mosaic:

100% Crop:

 

[Devin-M]

NGC 3324 MIRI Composite - Filters: 770W (Blue), 1130W (Green), 1280W (Red)

100% Crop:

100% Crop:

 

[Devin-M]

Messier 92 (Globular Cluster):

1 Sensor:

100% Crop:

 

[Devin-M]

IC 5332 Galaxy
MIRI Instrument, Filters: F1130W & F2100W

 

[pinball1970]

Hubble verses Webb- Earendel

 

[phinds]

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?

 

[Motore]

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.

 

[phinds]

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.

 

[pinball1970]

AH HA! I was looking for 90-degree flips/mirrors/whatever. Not very bright this morning. Thanks.

About 33deg

 

[phinds]

About 33deg

I'm up way too early this morning (long story) and I was only able to think in 90 degree increments.

 

[pinball1970]

This on Webb, not very old images of galaxies just dusty possibly!

https://arxiv.org/abs/2208.01816

I get alerts from space.com

https://www.space.com/james-webb-space-telescope-impostor-distant-galaxies

 

[Devin-M]

NGC 1365:

 

[pinball1970]

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.

 

[mfb]

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.

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.

 

[pinball1970]

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.

 

[Jonathan Scott]

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.

 

[sophiecentaur]

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.

 

[mfb]

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

 

[pinball1970]

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!”

 

[sophiecentaur]

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.

 

[Filip Larsen]

https://blogs.nasa.gov/webb/2022/09...its-first-ever-direct-image-of-distant-world/

For the first time, astronomers have used NASA’s James Webb Space Telescope to take a direct image of a planet outside our solar system. The exoplanet is a gas giant, meaning it has no rocky surface and could not be habitable.

 

[mfb]

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.

 

[Jonathan Scott]

100 AU away from its star at a distance of 400 AU.

I think you mean 400 light years.

 

[pinball1970]

A nice side by side comparison of Hubble and JWST. ORION NEBULA

 

[pinball1970]

Looks like there is a problem with MIRI.

This vid has good graphics and easier to post then try and summarize, too technical.



This article if the video does not play. Hopefully they can fix it.https://scitechdaily.com/problem-detected-on-the-james-webb-space-telescope-miri-anomaly/

EDIT: ..and the official statement from NASA which I could not access on my device yesterday.

https://blogs.nasa.gov/webb/2022/09/20/mid-infrared-instrument-operations-update/