APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

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APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by APOD Robot » Mon Aug 23, 2021 4:06 am

Image Abell 3827: Cannibal Cluster Gravitational Lens

Explanation: Is that one galaxy or three? Toward the right of the featured Hubble image of the massive galaxy cluster Abell 3827 is what appears to be a most unusual galaxy -- curved and with three centers. A detailed analysis, however, finds that these are three images of the same background galaxy -- and that there are at least four more images. Light we see from the single background blue galaxy takes multiple paths through the complex gravity of the cluster, just like a single distant light can take multiple paths through the stem of a wine glass. Studying how clusters like Abell 3827 and their component galaxies deflect distant light gives information about how mass and dark matter are distributed. Abell 3827 is so distant, having a <a hrec="ap130408.html">redshift</a> of 0.1, that the light we see from it left about 1.3 billion years ago -- before dinosaurs roamed the Earth. Therefore, the cluster's central galaxies have now surely all coalesced -- in a feast of galactic cannibalism -- into one huge galaxy near the cluster's center.

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by Ann » Mon Aug 23, 2021 5:54 am

APOD Robot wrote:

Is that one galaxy or three? Toward the right of the featured Hubble image of the massive galaxy cluster Abell 3827 is what appears to be a most unusual galaxy -- curved and with three centers. A detailed analysis, however, finds that these are three images of the same background galaxy -- and that there are at least four more images.
Abell 3827 Cannibal Cluster Gravitational Lens annotated.png

So where are the other four lensed images of that galaxy?

I have used a dark blue pen to mark three other blue lines or rings that I think are lensed versions of the same galaxy. I have marked two other blue galaxies with a cyan pen, because I think they may be lensed versions of another galaxy.

So what do the rest of you think? Where are the other four lensed versions of this galaxy?


The lensed galaxy appears to consist of a yellowish center surrounded by a large blue ring. So it is an early version of Hoag's Object, then?

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by VictorBorun » Mon Aug 23, 2021 7:57 am

However strange, the blue ring of Hoag's Object is not an image of a background galaxy gravitationally lensed by a foreground yellow globe in the center!

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by VictorBorun » Mon Aug 23, 2021 11:04 am

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by JohnD » Mon Aug 23, 2021 11:08 am

Today's blurb seems fixated on explaining gravitational lensing, and does so well, but at the expense of explaning the picture. For those who are unfamiliar with "Abell 3827", like me, it is the four bright objects near the centre. A link to, say, the Wiki entry would help: https://en.wikipedia.org/wiki/ESO_146-5

The blurb says that Abell 3827's light is redshifted to place it 1.3 BILLION light years away. Their light in the picture appears white, but as we know, astro picture colours are artificial. There are some VERY red objects in that same frame, bottom left and top right. There are more in the larger Wiki pic, so how far away are those??
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by VictorBorun » Mon Aug 23, 2021 12:21 pm

There seems to be a loss for words here.
Is ESO 146-5 a super-giant elliptical galaxy with 4 cores about to merge?
Or is it a cluster of 4 giant elliptical galaxies about to merge plus a dense cluster halo of rogue stars?
Anyway the monster proved to be easily tuned-off by going infra-red and radio range; so ESO 146-5 has no gas to speak of.
It has no young blue-and-ultraviolet stars either; so the bright ring of the background galaxy is easy to follow in blue despite of its redshift z=1.2414.

Now the amberish foreground four has z=0.099, enough to shift, say, limish 560 nm peak by 10% longer wavelength of 610 amberish

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by De58te » Mon Aug 23, 2021 1:35 pm

Ann wrote:
Mon Aug 23, 2021 5:54 am

So where are the other four lensed images of that galaxy?

I have used a dark blue pen to mark three other blue lines or rings that I think are lensed versions of the same galaxy. I have marked two other blue galaxies with a cyan pen, because I think they may be lensed versions of another galaxy.

So what do the rest of you think? Where are the other four lensed versions of this galaxy?

Ann
Just my un scholarly opinion but I think the four lenses are surrounding the 4 white galaxy centers. There is one under the white centre at left. Note that it consists of a blue bubble shape with one small centre galaxy. Now the other three are on the right. You had marked it as one lens but it is actually 3 connected. There is one bubble at top around one o'clock with a small galaxy at centre. There is one at bottom around 5 o'clock that is an upside down mirror image, and there is one in the middle, three o'clock, connecting the two.

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by orin stepanek » Mon Aug 23, 2021 1:42 pm

Abell3827Lens_Hubble_960.jpg
In my opinion; If it wasn't the same Galaxy, it would
have to be triplets! :mrgreen: Because they really look alike!
It's amazing what gravity lens can do!


946eff7741c6af1436dfe4975d31d95c.jpg
Cramming for a test!🧐
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by neufer » Mon Aug 23, 2021 2:15 pm

Click to play embedded YouTube video.
APOD Robot wrote:
Mon Aug 23, 2021 4:06 am


the cluster's central galaxies have now surely all coalesced -- in a feast of galactic cannibalism -- into one huge galaxy near the cluster's center.
Art Neuendorffer

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by Ann » Mon Aug 23, 2021 5:48 pm

JohnD wrote:
Mon Aug 23, 2021 11:08 am
Today's blurb seems fixated on explaining gravitational lensing, and does so well, but at the expense of explaning the picture. For those who are unfamiliar with "Abell 3827", like me, it is the four bright objects near the centre. A link to, say, the Wiki entry would help: https://en.wikipedia.org/wiki/ESO_146-5

The blurb says that Abell 3827's light is redshifted to place it 1.3 BILLION light years away. Their light in the picture appears white, but as we know, astro picture colours are artificial. There are some VERY red objects in that same frame, bottom left and top right. There are more in the larger Wiki pic, so how far away are those??
John
The picture was constructed using the following filters:

U, ultraviolet, 336 nm. NASA calls this an optical wavelength, but it really is invisible to humans. Light detected by this filter is mapped as purple.

V, visible light, 606 nm. This wavelength corresponds to yellow-orange light. Light detected by this filter has been mapped as blue.

I, 814 nm, infrared light. NASA calls this wavelength optical, but it is invisible to humans. Light detected by this filter has been mapped as green.

H, 1.6 μm, infrared light. Light detected by this filter has been mapped as red.

As long as we understand what the colors represent, I think we can more or less trust them. So why are some very distant objects blue, if they are so redshifted? First we must remember that objects that look blue in the picture may have reached us as yellow-orange light. (But there really may be some ultraviolet mixed in with the yellow-orange.) Second, any galaxy that looks blue in the picture was originally ablaze with brilliant ultraviolet light, and this light has been redshifted to yellow-orange light, or even to another wavelength of ultraviolet light. In short: Yes, back in the days when these galaxies were young (the way we see them), they were pumping massive amounts of ultraviolet light into space from extremely hot and massive stars, or in some cases, from an extremely brilliant active galactic center.

What about the very red galaxies? I'd say that while they are distant (obviously), they are not necessarily more distant than some of the small blue galaxies in the image. Their red color is not only due to distance and redshift-reddening, but also to the fact that at least some of these galaxies only emit longwave light. Either they are devoid of star formation, or else they are so dusty that the light from the hot stars inside them is completely smothered by dust. In fact, I think that one of both of the infrared filters used for this image are extremely good at detecting dust! We could be looking at dust when we see some of these red galaxies!

Bear in mind, too, that not all galaxies are created equal. Some are really big, while others are small. Some of the very red galaxies in the picture may well be quite large, and therefore much farther away than seemingly equally-sized seemingly nearby galaxies that are much less red.

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by Chris Peterson » Mon Aug 23, 2021 6:37 pm

Ann wrote:
Mon Aug 23, 2021 5:48 pm
JohnD wrote:
Mon Aug 23, 2021 11:08 am
Today's blurb seems fixated on explaining gravitational lensing, and does so well, but at the expense of explaning the picture. For those who are unfamiliar with "Abell 3827", like me, it is the four bright objects near the centre. A link to, say, the Wiki entry would help: https://en.wikipedia.org/wiki/ESO_146-5

The blurb says that Abell 3827's light is redshifted to place it 1.3 BILLION light years away. Their light in the picture appears white, but as we know, astro picture colours are artificial. There are some VERY red objects in that same frame, bottom left and top right. There are more in the larger Wiki pic, so how far away are those??
John
The picture was constructed using the following filters:

U, ultraviolet, 336 nm. NASA calls this an optical wavelength, but it really is invisible to humans. Light detected by this filter is mapped as purple.

V, visible light, 606 nm. This wavelength corresponds to yellow-orange light. Light detected by this filter has been mapped as blue.

I, 814 nm, infrared light. NASA calls this wavelength optical, but it is invisible to humans. Light detected by this filter has been mapped as green.

H, 1.6 μm, infrared light. Light detected by this filter has been mapped as red.

As long as we understand what the colors represent, I think we can more or less trust them.
It is still quite tricky to interpret the colors (which is why an astronomer would never use the color image to work with). Consider what it means to map something to purple. There is no such native color on our devices. So what they're doing is mixing the 336 nm data partly into blue, partly into red. Which means that data is scrambled in with the V channel and the IR channel. At best, the colors on the screen are highly ambiguous.
Chris

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by Fred the Cat » Mon Aug 23, 2021 6:58 pm

The pattern looks Lagrangian. Sort of like Einstein crosses. :?:

The article's math is heavy enough to distort space itself. :wink:
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by bystander » Mon Aug 23, 2021 7:15 pm

Ann wrote:
Mon Aug 23, 2021 5:48 pm

U, ultraviolet, 336 nm. NASA calls this an optical wavelength, but it really is invisible to humans. ...

I, 814 nm, infrared light. NASA calls this wavelength optical, but it is invisible to humans. ...
Optical vs visible

I take optical to mean ER that can be detected using "normal" optics, which includes IR and UV, as opposed to special purpose receivers such as radio, microwave, x-ray, or gamma-ray. Visible is just that narrower range of optics detectable by the human eye, between IR and UV.
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by Chris Peterson » Mon Aug 23, 2021 7:19 pm

bystander wrote:
Mon Aug 23, 2021 7:15 pm
Ann wrote:
Mon Aug 23, 2021 5:48 pm

U, ultraviolet, 336 nm. NASA calls this an optical wavelength, but it really is invisible to humans. ...

I, 814 nm, infrared light. NASA calls this wavelength optical, but it is invisible to humans. ...
Optical vs visible

I take optical to mean ER that can be detected using "normal" optics, which includes IR and UV, as opposed to special purpose receivers such as radio, microwave, x-ray, or gamma-ray. Visible is just that narrower range of optics detectable by the human eye, between IR and UV.
That's the usual understanding, although it's not uncommon to see "optical" used to mean "visible". So you have to hope for context sometimes.
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by johnnydeep » Mon Aug 23, 2021 8:56 pm

All in all, as clear as mud. I still don't know what ESO_146-5 is. The wikipedia article didn't help. And neither did the posts before me entirely explain it, some of which similarly bemoaned the lack of clarity. It seems like ESO_146-5 is supposed to be the four bright blobs in the center, and, sure, maybe they have indeed merged by now (in their frame of reference!), but why would we suddenly start taking such a hypothetical into account when to us, they are still 4 distinct - albeit quite visually similar - galaxies?

As for the original "much farther away" galaxy that was gravitationally lensed by ESO_146-5, is that seen elsewhere in this pic, in an unlensed form? Answering my own stupid question, I guess not since we're only seeing it at all due to it being directly behind ESO_146-5.

Finally, what's that big yellow-white shelled galaxy toward the bottom that looks like Darth Vader's TIE Fighter?
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by Chris Peterson » Mon Aug 23, 2021 9:32 pm

johnnydeep wrote:
Mon Aug 23, 2021 8:56 pm
All in all, as clear as mud. I still don't know what ESO_146-5 is. The wikipedia article didn't help. And neither did the posts before me entirely explain it, some of which similarly bemoaned the lack of clarity. It seems like ESO_146-5 is supposed to be the four bright blobs in the center, and, sure, maybe they have indeed merged by now (in their frame of reference!), but why would we suddenly start taking such a hypothetical into account when to us, they are still 4 distinct - albeit quite visually similar - galaxies?

As for the original "much farther away" galaxy that was gravitationally lensed by ESO_146-5, is that seen elsewhere in this pic, in an unlensed form? Answering my own stupid question, I guess not since we're only seeing it at all due to it being directly behind ESO_146-5.

Finally, what's that big yellow-white shelled galaxy toward the bottom that looks like Darth Vader's TIE Fighter?
I believe that ESO 146-5 is actually all four of the interacting galaxies. It was originally cataloged from plates that did not have enough resolution to separate them, and was identified as the brightest galaxy in the cluster. More current information in databases (like NED) categorize it as galaxy group, or multiple system. It is rather silly to talk about them having merged... that just plays into the fallacies surrounding what "now" means. They are four distinct, interacting, unmerged galaxies as we observe them, with a single designation.

We never see lensed galaxies in their unlensed form. They are simply too far away, in addition to generally being blocked by the lensing body or bodies.

The thing at the bottom looks like a barred spiral galaxy to me.
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by JohnD » Tue Aug 24, 2021 8:28 am

Thnak you, All, especially Ann and Chris!
I'm glad I asked the question, about colours and distance, because as I have said before, and IMHO of course, this should be a site with a scientific emphasis, where we can marvel at the beauty that is in astronomical science. The 'retouching' of star pictures we see here, is necessary for a lay audience - and I include myself! - but should be understood to be as potentially misleading as a moustache on the Mona Lisa.
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by johnnydeep » Tue Aug 24, 2021 1:03 pm

Chris Peterson wrote:
Mon Aug 23, 2021 9:32 pm
I believe that ESO 146-5 is actually all four of the interacting galaxies. It was originally cataloged from plates that did not have enough resolution to separate them, and was identified as the brightest galaxy in the cluster. More current information in databases (like NED) categorize it as galaxy group, or multiple system. It is rather silly to talk about them having merged... that just plays into the fallacies surrounding what "now" means. They are four distinct, interacting, unmerged galaxies as we observe them, with a single designation.

We never see lensed galaxies in their unlensed form. They are simply too far away, in addition to generally being blocked by the lensing body or bodies.

The thing at the bottom looks like a barred spiral galaxy to me.
Thanks.
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by markb212 » Thu Aug 26, 2021 4:44 pm

In most of the deep field images I've seen, any Milky Way stars in the field of view are "spiky" due to their relative brightness and optical effects of the telescope. I see two in this image. So are the rest of the points of light in this image extremely distant galaxies, or just really faint stars in our own galaxy? There's quite a dusting of them.

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by markb212 » Thu Aug 26, 2021 4:44 pm

In most of the deep field images I've seen, any Milky Way stars in the field of view are "spiky" due to their relative brightness and optical effects of the telescope. I see two in this image. So are the rest of the points of light in this image extremely distant galaxies, or just really faint stars in our own galaxy? There's quite a dusting of them.

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by Chris Peterson » Thu Aug 26, 2021 4:51 pm

markb212 wrote:
Thu Aug 26, 2021 4:44 pm
In most of the deep field images I've seen, any Milky Way stars in the field of view are "spiky" due to their relative brightness and optical effects of the telescope. I see two in this image. So are the rest of the points of light in this image extremely distant galaxies, or just really faint stars in our own galaxy? There's quite a dusting of them.
At this small FOV, virtually every source in the image is outside our galaxy.
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by markb212 » Thu Aug 26, 2021 5:02 pm

Just ... wow.
Thanks, Chris.

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by Chris Peterson » Thu Aug 26, 2021 5:30 pm

markb212 wrote:
Thu Aug 26, 2021 5:02 pm
Just ... wow.
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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by Ann » Thu Aug 26, 2021 5:38 pm

Chris Peterson wrote:
Mon Aug 23, 2021 9:32 pm

I believe that ESO 146-5 is actually all four of the interacting galaxies.
Cannibal Cluster Gravitational Lens 2 Annotated.png
Four versions of a lensed galaxy (blue), with four lensing elliptical galaxies
perfectly lined up. Image Credit: ESA/Hubble & NASA, R. Massey

Very interesting, Chris. What I find quite weird is that the four elliptical galaxies that provide the lens for the distant galaxy are so similar in size and brightness, and so regularly lined up. It's almost like looking at a galactic version of Orion's Belt, with Orion's Sword hanging below them.

Unless, of course, the objects that I have labeled 1,2.3 and 4 are not foreground elliptical galaxies, but brilliant centers of the background galaxy being lensed. (But lensed by what?)

The thing at the bottom looks like a barred spiral galaxy to me.
The thing at the bottom is a barred spiral galaxy, although with a very weak, non-starforming set of spiral arms. The galaxy is well on its way to becoming an S0 (lenticular) galaxy.

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Re: APOD: Abell 3827: Cannibal Cluster Lens... (2021 Aug 23)

Post by Chris Peterson » Thu Aug 26, 2021 6:54 pm

Ann wrote:
Thu Aug 26, 2021 5:38 pm
Chris Peterson wrote:
Mon Aug 23, 2021 9:32 pm
I believe that ESO 146-5 is actually all four of the interacting galaxies.
Very interesting, Chris. What I find quite weird is that the four elliptical galaxies that provide the lens for the distant galaxy are so similar in size and brightness, and so regularly lined up. It's almost like looking at a galactic version of Orion's Belt, with Orion's Sword hanging below them.

Unless, of course, the objects that I have labeled 1,2.3 and 4 are not foreground elliptical galaxies, but brilliant centers of the background galaxy being lensed. (But lensed by what?)

No. Objects 1-4 are foreground galaxies (z = 0.1) lensing the background galaxy (z = 1.24). The redshift of the four interacting galaxies is the same as that of the other galaxies seen in the cluster, and so far from that of the lensed galaxy that there is no chance of confusing them at all.
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