Need help finding source information on blue Einstein Rings

Mar 30, 2020
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In the last 20 years, people have noticed that some Einstein Rings appear blue, like in this example from a Hubble news release: https://hubblesite.org/contents/news-releases/2005/news-2005-32.html. While this is sometimes due to postprocessing coloring techniques, other times, it is unknown why lensed galaxies appear blue or shift frequency.

Academics have written papers and explanations for this. Here are two papers:

"Why is an Einstein Ring Blue?":
https://arrow.tudublin.ie/engscheleart2/19/

"Bending of Light Near a Star and Gravitational Red/Blue Shift : Alternative Explanation Based on Refraction of Light":
https://arxiv.org/abs/physics/0409124

I do not know how people noticed this phenomenon. Was it through a direct observation or by analyzing frequency data? I checked the citations in each of the above papers, but neither specifically cited when or where researchers noticed Einstein Rings appearing blue or changing a lensed galaxy's apparent frequency.

I would like help finding data or images on an Einstein Ring that made the lensed galaxy appear blue or to change light frequency. I believe that a lot of the data from research satellites and telescopes, such as the Hubble Space Telescope, is public, but I do not know how to navigate and find what I am looking for. I would appreciate it if anyone could show us the data from observations by Hubble or any other telescope which shows an Einstein Ring making the lensed galaxy shift blue or shift in apparent frequency.

Much appreciated.
 
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IG2007

"Don't criticize what you can't understand..."
Apr 5, 2020
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Since 1998, when the first complete Einstein ring was observed, many more complete or partially complete Einstein rings have been observed in the radio and infrared spectra, for example, and by the Hubble Space Telescope in the optical spectrum. However, in the latter case, it is observed that the rings are blue providing the light is not red shifted.

I got it from one of your URLs : https://arrow.tudublin.ie/engscheleart2/19/

Well, as far as I know English, I guess the lines mean that, in all, radio, infrared and optical spectra, Einstein Rings appeared blue when it was first observed. You have got your answer.
 
Mar 30, 2020
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Thank you for your reply. Is there frequency data or a report that mentions a galaxy's frequency shifting after being lensed?
Since 1998, when the first complete Einstein ring was observed, many more complete or partially complete Einstein rings have been observed in the radio and infrared spectra, for example, and by the Hubble Space Telescope in the optical spectrum. However, in the latter case, it is observed that the rings are blue providing the light is not red shifted.

I got it from one of your URLs : https://arrow.tudublin.ie/engscheleart2/19/

Well, as far as I know English, I guess the lines mean that, in all, radio, infrared and optical spectra, Einstein Rings appeared blue when it was first observed. You have got your answer.
[/QUOTE]
 
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Jun 1, 2020
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Thank you for your reply. Is there frequency data or a report that mentions a galaxy's frequency shifting after being lensed?
Your paper referenced seems to have at least one explanation, though I haven’t read it beyond the abstract.

One site I found tries to argue that the background galaxy is blue, but though they are likely correct, the expansion of space makes more red than blue. Thus, some refraction effect seems to be happening. Blue will bend more than red, so perhaps there is an interesting effect where the greatest magnification effect that we would observe is for blue light. [The other colors are there but not bent in our direction.] If so, then perhaps a test would be to find some red lens effects where our alignment is weaker.

If this idea is valid, then I thinkthe blue we see is actually UV that has been redshifted to blue due tothe cosmological expansion.
 
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An analogy may help perhaps. When we see a rainbow, we see refraction from thousands of water droplets due the wall of light rain. Each color comes to us from a slightly different location due to refraction, where wavelength affects the refraction angle.

But what if the droplets were only located where we see blue? We would only see blue, right!

The grav lens isn’t a uniform wall of refractive elements, thus we are limited in seeing the color tha bends the most at this limited region, perhaps.
 
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An analogy may help perhaps. When we see a rainbow, we see refraction from thousands of water droplets due the wall of light rain. Each color comes to us from a slightly different location due to refraction, where wavelength affects the refraction angle.

But what if the droplets were only located where we see blue? We would only see blue, right!

The grav lens isn’t a uniform wall of refractive elements, thus we are limited in seeing the color tha bends the most at this limited region, perhaps.
Thank you for the analogy. Right on the point of relation between light bending and its frequency. Many try to explain Gravitational Lensing / Einstein Ring by a ray of light going through a piece of glass. Here is one:

"In any event, the strength of a gravitational field can distort light, just as a piece of glass can. "


The problem is there is no variable of frequency (or wavelength) of light in General Relativity Theory. According to this theory, light should bend the same in a curving space regardless its frequency . That is different from the refraction of light after it going through a piece of glass (or rainbow). However, the distorted image after Gravitational Lensing / Einstein Ring seems to show that the different refractions of the various wavelengths (or frequency) spread them apart as in a rainbow, so we observe frequency shift.

It is strange, unless the light and gravity has this relation according to the new theory below. Frequency of light is a variable here in a gravitational lensing.

 
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IMO, and I'm more guessing than not, the attachment might explain my point of view.



There is some exaggeration for effect here, of course, but vast distances are needed to see color change due to the tiny refraction effect of grav lenses.

So, those more inline with the Source and Cluster will likely see the greater refraction effects, which are always in the blue portion of the spectrum.

But I included position 2 for Earth. If my view is correct and we were in position 2, then we should also see more red since we would be more offset from the center line.

Here is a page that shows (see their third figure) color variation. Notice that the red circled areas are the more distorted (ie less inline) views and they reveal (due to refraction) more red color than blue.

What I still don't understand is how such vastly distant sources (e.g. quasars) that we know are receding at incredible speeds due to expansion, have major redshifts, can still have so much blue light. It's possible that, since we see them at their early ages, that UV is very strong, so the cosmological redshift is producing strong blue light, perhaps.
 
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Below is a better drawing, I think, than above because it reveals why the tight, more complete rings are blue vs. red.



Since blue bends the most in refraction, then Earth will more likely encounter blue rings, as shown. If Earth is in either position 2 or 3, then only a partial ring is likely.

If, however, the distance A is increased and, probably, the distance B is also increased, then perhaps the micro-bending angle will allow both reds to converge on Earth, but I suspect Earth would need to be a number of billion lightyears more distant. [The micro-arcseconds of bending is not an unknown for a given gravity lens, so some simple trig may be all that is necessary to match distance A an B to get convergence.]

If red is seen on both sides of the grav lens, then both A and B would be close to the Goldylocks combination. In that case, the blue light would have had a focal point somwhere within the B distance and would now be diverging around the Earth, hence no blue would be seen, only the red-end colors.
 
Jun 1, 2020
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"In any event, the strength of a gravitational field can distort light, just as a piece of glass can. "


The problem is there is no variable of frequency (or wavelength) of light in General Relativity Theory. According to this theory, light should bend the same in a curving space regardless its frequency . That is different from the refraction of light after it going through a piece of glass (or rainbow). However, the distorted image after Gravitational Lensing / Einstein Ring seems to show that the different refractions of the various wavelengths (or frequency) spread them apart as in a rainbow, so we observe frequency shift.

It is strange, unless the light and gravity has this relation according to the new theory below. Frequency of light is a variable here in a gravitational lensing.
Yes, and even the first link it isn't saying that it's wrong to treat light as bending. The point is one of semantics. Light never bends; it is responding to the change in the medium it is passing through (spacetime or glass). Thus one could argue that light doesn't bend through a glass lens, but it's the medium difference that makes it appear as if it is bending.

Regardless, from what I've seen, wavelength determines how much light will bend when passing through a strong gravitational gradient (ie gravity lens).
 
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