APOD: Abell 2218: A Galaxy Cluster Lens (2010 Jun 20)

[APOD Robot]

Abell 2218: A Galaxy Cluster Lens

Explanation: What are those strange filaments? Background galaxies. Gravity can bend light, allowing huge clusters of galaxies to act as telescopes, and distorting images of background galaxies into elongated strands. Almost all of the bright objects in this Hubble Space Telescope image are galaxies in the cluster known as Abell 2218. The cluster is so massive and so compact that its gravity bends and focuses the light from galaxies that lie behind it. As a result, multiple images of these background galaxies are distorted into long faint arcs -- a simple lensing effect analogous to viewing distant street lamps through a glass of wine. The cluster of galaxies Abell 2218 is itself about three billion light-years away in the northern constellation of the Dragon (Draco). The power of this massive cluster telescope has allowed astronomers to detect a galaxy at the distant redshift of 5.58.

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[Parker]

Could we see this image with a mouse-over that labels which objects are Abell 2218, and which are lensed galaxies? Clarity for the uninitiated. Thanks. Great image!

[rwarner]

Wonderful detail!
Is that a red dwarf in the upper part of the picture, just to the right of center?
If it's a galaxy, that must be some red shift!

Ronnie Warner

[Beyond]

I've just recently seen this Apod somewhere. But there was a slight difference. The one that i saw said something about the oldest Galaxy found so far and i think it said that it was a faint red spot located lower right of center. I could not tell it was there when i looked, but that does not mean anything.
Also this picture seems to be a little more to the left then the one i saw.

[bystander]

Abell 2218: A Galaxy Cluster Lens (2008 Feb 10)

Click to view full size image

Gravity can bend light, allowing huge clusters of galaxies to act as telescopes. Almost all of the bright objects in this Hubble Space Telescope image are galaxies in the cluster known as Abell 2218. The cluster is so massive and so compact that its gravity bends and focuses the light from galaxies that lie behind it. As a result, multiple images of these background galaxies are distorted into long faint arcs -- a simple lensing effect analogous to viewing distant street lamps through a glass of wine. The cluster of galaxies Abell 2218 is itself about three billion light-years away in the northern constellation of the Dragon (Draco). The power of this massive cluster telescope has allowed astronomers to detect a galaxy at redshift 5.58, the [url=ahttp://apod.nasa.gov/apod/p970731.html]most distant galaxy[/url] yet measured. This young, still-maturing galaxy is faintly visible to the lower right of the cluster core.

[moonstruck]

Lawdy, Lawdy, Miss Clawdy, It's hard to believe all this is happening out there. We just sit here spinning around on our little bitty planet earth thinkin we is the most important happening in the whole wide universe and really we ain't doodly squat in the whole scheme of things. Rats, I think I'll gota bed.

[Ann]

That's a beautiful and impressive image. It would be fun to know exactly how many background galaxies have had their shapes drawn into long filaments by the cluster's humongous gravity, and it would be fun to know which of the filaments actually "belong" to the same background galaxy.

Ann

[geckzilla]

Could we see this image with a mouse-over that labels which objects are Abell 2218, and which are lensed galaxies? Clarity for the uninitiated. Thanks. Great image!

They probably won't add a mouseover, but it's easy to explain which they are. The elongated, skinny galaxies which kind of form a circle around the foreground cluster are the lensed ones. You can find 10 or 15 different stretched images of the galaxies but they are actually multiple images of only a few galaxies, though I wouldn't know the exact number.

[neufer]

Lawdy, Lawdy, Miss Clawdy, It's hard to believe all this is happening out there. We just sit here spinning around on our little bitty planet earth thinkin we is the most important happening in the whole wide universe and really we ain't doodly squat in the whole scheme of things.

• ------------------------------------------------------------------------------
  • ___ The Adventure of the Six Napoleons
  The spat where the fragments of the bust had been found was only a few hundred yards away. For the first time our eyes rested upon this presentment of the great emperor, which seemed to raise such frantic and destructive hatred in the mind of the unknown. It lay scattered, in splintered shards, upon the grass. Holmes picked up several of them and examined them carefully. I was convinced, from his intent face and his purposeful manner, that at last he was upon a clue.
  
  "Well?" asked Lestrade.
  
  Holmes shrugged his shoulders.
  
  "We have a long way to go yet," said he. "And yet--and yet-- well, we have some suggestive facts to act upon. The possession of this trifling bust was worth more, in the eyes of this strange criminal, than a human life. That is one point. Then there is the singular fact that he did not break it in the house, or immediately outside the house, if to break it was his sole object."
  
  "He was rattled and bustled by meeting this other fellow. He hardly knew what he was doing."
  
  "Well, that's likely enough. But I wish to call your attention very particularly to the position of this house, in the garden of which the bust was destroyed."
  
  Lestrade looked about him.
  
  "It was an empty house, and so he knew that he would not be disturbed in the garden."
  
  "Yes, but there is another empty house farther up the street which he must have passed before he came to this one. Why did he not break it there, since it is evident that every yard that he carried it increased the risk of someone meeting him?"
  
  "I give it up," said Lestrade.
  
  Holmes pointed to the street lamp above our heads.
  
  "He could see what he was doing here, and he could not there. That was his reason."
  
  
  "By Jove! that's true," said the detective. "Well, Mr. Holmes, what are we to do with that fact?"
  
  "To remember it--to docket it. We may come on something later which will bear upon it.

------------------------------------------------------------------------------

• ____ A Bell - 221B [Baker Street]

<<"Joseph BELL, JP, DL, FRCS (2 December 1837 – 4 October 1911) was a Scottish lecturer at the medical school of the University of Edinburgh in the 19th century. He is perhaps best known as an inspiration for the literary character Sherlock Holmes.

He was a great-grandson of Benjamin Bell, a forensic surgeon. In his instruction, Bell emphasized the importance of close observation in making a diagnosis. To illustrate this, he would often pick a stranger and, by observing him, deduce his occupation and recent activities. These skills caused him to be considered a pioneer in forensic science (forensic pathology in particular) when science was not often used in the investigations of crimes.

Arthur Conan Doyle met Bell in 1877, and served as his clerk at the Edinburgh Royal Infirmary. Doyle later went on to author a series of popular stories featuring Sherlock Holmes, who Doyle stated was loosely based on Bell and his observant ways. Bell was aware of this inspiration and took some pride in it. Bell served as personal surgeon to Queen Victoria whenever she visited Scotland.>>

------------------------------------------------------------

<<Inspector Lestrade of Scotland Yard brings Holmes a seemingly trivial problem about a man who shatters plaster busts of Napoleon. One was shattered in Morse Hudson’s shop, and two others, sold by Hudson to a Dr. Barnicot, were smashed after the doctor’s house and branch office had been burgled. Nothing else was taken. In the former case, the bust was taken outside before being broken.

Holmes knows that Lestrade’s theory about a Napoleon-hating lunatic must be wrong. The busts in question all came from the same mould. Why is he breaking them?

The next day, Lestrade calls Holmes to a house where there has been yet another bust-shattering, but there has also been a murder. Mr. Horace Harker found the dead man on his doorstep after investigating a noise. His Napoleon bust was also taken by a burglar entering through a window. It, too, was from the same mould. Also, a photograph of a rather apish-looking man is found in the dead man’s pocket.

The fragments of Harker's bust are in the front garden of an empty house up the street. Obviously the burglar wanted to see what he was doing, for there is a streetlamp here, whereas the bust could have been broken at another empty house nearer Harker’s, but it had been dark there.

The mystery is at last laid bare after Holmes offers £10 to the owner of the last existing bust, making him sign a document transferring all rights and ownership of the bust to Holmes. After the seller has left, Holmes smashes the bust and among the plaster shards is a gem, the black pearl of the Borgias.>>

[León]

The photon has no mass therefore can not be attracted to any body. I believe that the gases are concentrated in the cluster. It is a natural magnifying glass as they are ordered to do so and closer to the vision of distant objects, and in the absence distort as the bottom when they are not sorted.


In the cluster there are different areas, some distort and make other zoom lens

[rstevenson]

The photon has no mass therefore can not be attracted to any body. ...

The path a photon takes is bent by gravity. See this (and many other) articles.

Rob

[Chris Peterson]

The photon has no mass therefore can not be attracted to any body.

You are mistaken in your understanding of photons. They do have mass. You can calculate it directly from the energy equivalence, or from the momentum-energy relationship. Photons have a rest mass of zero, which describes something of the particle properties, but has no bearing on their observed behavior, since a photon cannot actually be at rest.

Because a photon has a mass equivalence, you can actually apply Newtonian gravity calculations and come close to the observed behavior of gravity lenses. There are various relativistic effects that cause some deviation from observation, however. For an accurate description, it is necessary to use GR, and consider the way in which mass and energy interact in spacetime. The distortion of space by the mass of the foreground material causes the path of distant photons to be altered.

[enb]

Why are the thin, lensed galaxies in the pic blue? Wouldn't you expect the lensed galaxies to be extremely red, redder than the orangish abbel galaxies?

[jefflass]

One is under the impression, according to Herr Albert Einstein, that gravity warps SPACE-TIME but has no direct effect on light. This is always illustrated by a weight on a rubber sheet in which a heavier weight creates a deeper warp. When light traveling through space-time (the rubber sheet) encounters a warp in that space-time, it merely follows the curvature imposed by the warp. In other words, warped space-time seems to act like a lens diverting photons passing through the warpiness just like a glass lens. [Near black holes the space-time is warped so dramatically in such a small area that any escaping internal light is curved back into the holes.] Yet it would seem that to act like a lens, a space-time warp would need to be denser than the surrounding unaffected space-time medium. For some reason one hears little about warped space-time density increases. Maybe the dense lens analogy is totally inappropriate because some other unknown physical aspect of warped space-time is really causing the effect.

[neufer]

Why are the thin, lensed galaxies in the pic blue?
Wouldn't you expect the lensed galaxies to be extremely red, redder than the orangish abbel galaxies?

Elliptical galaxies are naturally orange.

The blue (star-forming) spiral galaxies at intermediate redshift (z=1-2.5)
probably originally had their peak energy output in the ultraviolet.

<<Abell 2218 is a cluster of galaxies about 2 billion light-years away in the constellation Draco. Acting as a powerful lens, it magnifies and distorts all galaxies lying behind the cluster core into long arcs. The lensed galaxies are all stretched along the cluster's center and some of them are multiply imaged. Those multiple images usually appear as a pair of images with a third — generally fainter — counter image, as is the case for the very distant object.



The color of the lensed galaxies is a function of their distances and types. The orange arc is an elliptical galaxy at moderate redshift (z=0.7). The blue arcs are star-forming galaxies at intermediate redshift (z=1-2.5). The encircled very red pair is the newly discovered star-forming galaxy at about redshift 7.>>

[León]

The photon always drawn the line, if not impossible to do with definition would be galaxies away, we'd see the warped universe, something like that shows the image of the cluster. Ergo the gravity does not reach the photon.

[Chris Peterson]

The photon always drawn the line, if not impossible to do with definition would be galaxies away, we'd see the warped universe, something like that shows the image of the cluster. Ergo the gravity does not reach the photon.

I think you need to check the definition of "ergo". <g>

[León]

Sorry for using the Latin word "ergo", commonly used in Castilian corresponding later (por tanto- luego-pués)

[neufer]

Sorry for using the Latin word "ergo", commonly used in Castilian corresponding later (por tanto- luego-pués)

The real point is that the gravitational bending of light is a predicted and measured fact of life:

[Chris Peterson]

Sorry for using the Latin word "ergo", commonly used in Castilian corresponding later (por tanto- luego-pués)

The problem wasn't the Latin... the word means the same thing in English: therefore or thus it follows. The problem was that your conclusion didn't follow your premise. Photons are affected by gravitational fields- a fact that follows from solid theory and which is fully supported by observation.

[León]

The conclusion is supported by what comes out of the picture. Corresponds to a larger work that I have published in Castilian. Mr. Petersen, please mark the solid theories based on observation than those of Eddington vitiated by apparent falsehood to pretend to support the predictions of Einstein. From already thank you very much.

[Chris Peterson]

The conclusion is supported by what comes out of the picture. Corresponds to a larger work that I have published in Castilian. Mr. Petersen, please mark the solid theories based on observation than those of Eddington vitiated by apparent falsehood to pretend to support the predictions of Einstein. From already thank you very much.

If you're competent enough to have published works on this matter in peer reviewed journals, you're certainly aware of the evidence that supports GR. Einstein doesn't need me to defend him!

[León]

The publication is a book, Cosmogony, Cosmological with 45 positions, whose exposure may give rise to further differences with some of the experts.

[Martin]

Can gravitational lensing alter the red-shift of light?

[neufer]

Can gravitational lensing alter the red-shift of light?

Very minimally.

It's like a spacecraft doing a flyby of the planet Jupiter:

1) So far as Jupiter is concerned the spacecraft exits with exactly the same speed |V_x| as it entered with |V_e|.

2) However, since Jupiter is moving with velocity vector V_J vis-a-vis the solar system the dynamical exit speed |V_x+V_J| does not necessarily equal the entrance speed |V_e+V_J|. This fact has been used extensively to boost the speed of all spacecraft passing beyond Jupiter (by intentionally flying behind Jupiter).

An extreme red-shift example might be if we shot a laser beam at a black hole of a given redshift z_b. The returning laser beam that had U-turned around the back of the black hole would come back with twice the black hole's redshift = 2 z_b. But this is extremely far removed from the actual situation one has in observed gravitational lensing cases.