Multiple images in gravitaional lensing

In summary: So the lensing is due to the geometry of the galaxy, not the light itself?The lensing is due to the geometry of the galaxy, not the light itself.
  • #1
Agerhell
157
2
On the subject of gravitational lensing there seems to be two rather different phenomena. The "arc" phenomena seems rather plausible to me, if light is affected by gravity which is natural then there should be able to get that kind of behaviour.

But the multiple imaging stuff, seems rather strange to me, why does it occur?

If you look on the wikipedia page for gravitational lensing:
http://en.wikipedia.org/wiki/Gravitational_lens

There are three examples of arc-like phenomena, but there is also one exampel of multiple images, the so called "Einsteins Cross".

http://en.wikipedia.org/wiki/Einstein_Cross

Where, for some reason, there is what looks like for different quasars (or stars, I guess you need some kind of spectra to see that they are quasars) which is said to be four different images of the same Quasar.

Besides from explaining it here, it would be helpful if someone who knows more than me could write something on this on Wikipedia. There is basically only one and not very informative sentence on the subject there.
 
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  • #2
You can see multiple images by looking through funny-shaped pieces of glass easily. Why should gravitational lensing be any different? The foreground galaxy is not perfectly symmetrical, that's all.
 
  • #3
True that, but what is the significance of there being four, why not five and a half?
 
  • #4
Basically, the lensing is such that different line-of-sight light rays gets bent to the same destination (your telescope).

The number of images is determined by the geometry. Sometimes you see the images get smeared out too.
 
  • #5
Right the geometry. Doesn't the cross suggest a four-fold geometry, like a square or octahedron of sorts?
 
  • #6
Matterwave said:
Basically, the lensing is such that different line-of-sight light rays gets bent to the same destination (your telescope).

The number of images is determined by the geometry. Sometimes you see the images get smeared out too.

Well then, what is so special about "Huchra´s lens", the galaxy that according to wikipedia is the lens in this particular case?

What is it about Huchra´s lens that creates four images?

According to this picture from the European Space Observatory it looks like an ordinary galaxy:
http://www.eso.org/public/images/eso0847a/
 
  • #7
Imagine the gravitational field of this galaxy was octahedral in shape. It would have to be a hyperbolic octahedron because gravity is hyperbolic. Next the octahedron would have to be aligned with us in such a way that the four images pass around to produce this pattern.

http://bulatov.org/math/1101/img/ideal_octahedron.jpg

This is what I meant when I said a four-fold octahedral symmetry.
 

1. What is gravitational lensing?

Gravitational lensing is a phenomenon in which the light from a distant object is bent as it passes through a massive object, such as a galaxy or a cluster of galaxies. This bending of light creates multiple images of the distant object, allowing us to see it from different perspectives.

2. How are multiple images formed in gravitational lensing?

Multiple images are formed when the light from a distant object is bent by the gravitational pull of a massive object, creating distorted and magnified images. These images are formed due to the different paths that the light takes as it travels around the massive object.

3. What is the difference between strong and weak gravitational lensing?

Strong gravitational lensing occurs when the massive object is large enough and close enough to the distant object to create distinct, highly magnified images. Weak gravitational lensing occurs when the effects of lensing are subtle and require statistical analysis to detect.

4. How do scientists use multiple images in gravitational lensing to study the universe?

Multiple images in gravitational lensing provide valuable information about the distribution of mass in the universe, as well as the properties of dark matter. By analyzing the distortions and magnifications of these images, scientists can map the distribution of mass and study the effects of dark matter.

5. Can gravitational lensing be used to discover new objects?

Yes, gravitational lensing can be used to discover new objects that would otherwise be too faint to be seen. These objects can include distant galaxies, quasars, and even planets. Gravitational lensing also allows us to study the properties of these objects in greater detail than would be possible without the lensing effect.

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