Starship Asterisk*

by **Chris Peterson** » Wed Sep 23, 2009 5:02 pm

Case wrote:If this analogy holds any truth, then could it be that we Earthlings are in a spot where we see some gravitational lensed background galaxy very bright (disregarding its distorted shape for now), while some other gravitational lensed background galaxy is much dimmed?

Clearly, any sort of lens, including a gravitational lens, is taking what is essentially an omnidirectional radiator (the background galaxy) and in one particular direction (through the optical axis of the lens) it is producing a non-omnidirectional output. So your position is important. Planet X will likely see something very different. This is self evident if you consider sliding far enough sideways that the intervening lens is no longer between you and the background galaxy. In that case, you'll either see the galaxy directly, or no galaxy at all (since you won't be taking advantage of the large effective aperture of the lens).

by **Case** » Wed Sep 23, 2009 8:43 am

Chris Peterson wrote:There is no "bright spot". The image with the glass shows a real image focused on a screen. That is not in the slightest equivalent to the images we make of lensed galaxies, unless you happen to be referring to an ant crawling around on the print or your monitor.

Allow me to re-phrase a portion of my previous post, for I may not have been as clear as I can:

I imagine an observer on planet "X", like an ant in a bright spot on my projection paper, as being able to see a gravitational lensed background galaxy unusually bright. And I imagine a different observer on planet "Y", like an ant in a dark spot on the piece of paper, as seeing very little of the same background galaxy. The purpose of my little desktop experiment was to show the uneven distribution of light (light-intensity) done by lensing.
If this analogy holds any truth, then could it be that we Earthlings are in a spot where we see some gravitational lensed background galaxy very bright (disregarding its distorted shape for now), while some other gravitational lensed background galaxy is much dimmed?

by **Chris Peterson** » Tue Sep 22, 2009 10:24 pm

Case wrote:
A projection of a light source, distorted through a "lens" (glass), shows brighter areas (brighter than directly lit by the same light source) and darker areas (perhaps as dark as a shadow from an opaque object, leaving just ambient light). Is the same true for the gravitational lens effect?
I imagine an observer in such a bright spot as being able to see a gravitational lensed background galaxy unusually bright, and an observer in such a dark spot as seeing very little of the same background galaxy. Does it actually work something like this? Can it be that we miss some of those background galaxies because light is mostly bended away from us?

There is no "bright spot". The image with the glass shows a real image focused on a screen. That is not in the slightest equivalent to the images we make of lensed galaxies, unless you happen to be referring to an ant crawling around on the print or your monitor. Any observer along the path between your eye and a dark area as seen by your eye would simply be imaging the scene from a slightly different viewpoint.

We do miss light from the background galaxies- most of it, in fact. Just like when you take a picture of something you miss most of the light.

by **neufer** » Tue Sep 22, 2009 6:30 pm

Case wrote:
A projection of a light source, distorted through a "lens" (glass), shows brighter areas (brighter than directly lit by the same light source) and darker areas (perhaps as dark as a shadow from an opaque object, leaving just ambient light). Is the same true for the gravitational lens effect?
I imagine an observer in such a bright spot as being able to see a gravitational lensed background galaxy unusually bright, and an observer in such a dark spot as seeing very little of the same background galaxy. Does it actually work something like this? Can it be that we miss some of those background galaxies because light is mostly bended away from us?

I believe so except that an observer located in such a bright spot would probably see multiple images of a background galaxy (often blurred together such as in the "APOD 2009 Sept 21"). Likewise there must be galaxies we simply can't see from here.

http://en.wikipedia.org/wiki/Cloak_of_invisibility wrote:
<<A cloak of invisibility is a theme that has occurred in fiction, and is a device which is under some scientific inquiry. American group of scientists say that a cloak could be very similar to the invisibility cloak in Harry Potter. The design calls for tiny metal needles to be fitted into a hairbrush-shaped cone at angles and lengths that would force light to pass around the cloak. This would make everything inside the cone appear to vanish because the light would no longer reflect off it. "It looks pretty much like fiction, I do realize, but it's completely in agreement with the laws of physics," said lead researcher Vladimir Shalaev, a professor of electrical and computer engineering at Purdue. "Ideally, if we make it real it would work exactly like Harry Potter's invisibility cloak," he said. "It's not going to be heavy because there's going to be very little metal in it.">>

by **billMe** » Tue Sep 22, 2009 4:46 pm

IAC, this is one of my favorite images

by **Star*Hopper** » Tue Sep 22, 2009 3:18 pm

"Although curious, one initial response was to avoid commenting on the arc because nothing like it had ever been noted before. In the mid-1980s, however, better images allowed astronomers to identify the arc as a prototype of a new kind of astrophysical phenomenon -- the gravitational lens effect ..."

Y'know, astronomers (some of them at least) can be a piece of work - argumentive, never fault, and rampantly jealous.
"...avoid commenting because nothing like it had ever been noted before", indeed. "Let's wait & see what others say - let them be the fool."

Yet, once it's deduced, watch 'em all scramble trying to claim "I was first"....that's the real circus.

~S*H

by **kovil** » Tue Sep 22, 2009 3:12 pm

Thanks DavidL, I missed the mouse-over feature, and it sure shows things much better !
There are several clearly arcing, what shall we call them?, images?, especially the 9 o'clock pair, and several more that are suggesting the edge of a sphere centered in the middle of the photo. But there are more images that suggest a different orientation to their curvature, or even lack of curvature in other small images, almost straight lines.

Whatever is happening optically here, it gives us a very large clue to the nature of the reality of how light interacts with whatever is causing this effect !
Unless these strange appearing images are actually what we are seeing, and we don't yet understand why they are this shape.

The James Webb space telescope will be very busy !!!
Cheers to APOD for posting this photo !

And on second viewing, geckzilla, I got carried away in my rant.
Tho it has always been curious as to why do globular clusters seem to be predominantly, if not exclusively, yellow spectrum stars, with a severe absence of blue spectrum stars, compared to spiral galaxies.

The 'Salvador Dali' galaxy at 3 o'clock, is now looking more like two galaxies that got severely 'stuck' to each other and stretched a long bridge of material between themselves as they moved apart.
Like two pocket watches with time stretching between them after first contact, akin to butter spread over too much bread ! (ahh, could I only find my references as fast as neufer on the web !)

I also didn't read Case's second post about light being focused brighter and waned weaker by the intervening object, to the background observers or the paper in his example. An excellent point ! We may be in a bright spot.

by **DavidLeodis** » Tue Sep 22, 2009 11:16 am

Clicking on the APOD (or using the "pictured above" link in the explanation) brings up a wider field-of-view image that has some interesting looking galaxies that are not seen in the cropped version of that which is used for the APOD. 8)

by **calibrator** » Tue Sep 22, 2009 2:36 am

ABELL 370:
I took a closer look at the Abell 370 photo and it appears that there is more than one lensing effect going on as though multiple sources are bending light from different objects. It looks to me somewhat like bubbles similar to placing different types and sizes of lenses behind the larger. In a clear crystal sphere there would be reflections, shadows or ghosts on the opposite side of the sphere. In this photo some of those are disrupted by something else which is effecting the light also. Perhaps another gravitational anomaly? Is it possible to plot these effects?

by **geckzilla** » Mon Sep 21, 2009 5:07 pm

I disagree with you, kovil. There's not a single individual star nearly visible in any of those galaxies at all. I think you are mistaken on multiple accounts.

by **kovil** » Mon Sep 21, 2009 4:24 pm

This APOD (I still love the photos !, guys.) is yet another example of how 'lamestream astrophysics and cosmology' is living in the La La Land of their mathematical illusions and fantasies.

To wit: " . . . better images allowed astronomers to identify the arc as a prototype of a new kind of astrophysical phenomenon, the gravitational lens effect of an entire cluster of galaxies on a background galaxy. Today, we know that this arc actually consists of two distorted images of a fairly normal galaxy that happened to lie far behind the huge galaxy cluster, Abell 370."

If this 'gravitationally lensed' far distant galaxy has bright blue knots of star formation in progress in its spiral arms, how can we see that so clearly ? As to almost be able to see individual stars with a little more resolution, yet the supposedly foreground galaxies of Abell 370 are all smeared yellow smudges in the photo ! It would seem unlikely that among all of the Abell 370 galaxies that not a one has any bright blue star regions. Even magnifying the far distant galaxy would not make the star regions in its spiral arms that much more distinct, while the foreground galaxies all look so indistinct.

I completely disagree with the concept of gravitational lensing as to what's happening here, but that said, this photo sure shows something very interesting is happening optically to the light we are receiving !!!
It seems somewhat unlikely that the 'stretched galaxy' is actually in that shape, and the two likewise stretched images at about 9 o'clock and two more at 1 and 2 o'clock respectively look suspiciously like the same image of the stretched galaxy, yet in a much smaller version (getting a z-shift reading and a spectroscopic analysis would be good to do, if possible on that small of an object with no interference of in-between objects) .

That's it from this neck of the stellar woods ! Keep up the good work guys, and don't let mathematical unicorns spear you to the wall of 'moron of the week' !

by **aglosson** » Mon Sep 21, 2009 2:35 pm

One thing that struck me about this image was on the left side. There are 2 vertically positioned galaxies, with slight curvature (curved around the center of the overall image). The topmost image appears to be a mirror (top to bottom swap) with the bottom image of that pair. If that is the case, how is that possible with gravitational lensing? I didn't think that any sort of transmission optics could do that? Are they really 2 separate galaxies, but which look virtually identical? Are the spectra the same?

I'm curious.

by **Case** » Mon Sep 21, 2009 11:03 am

A projection of a light source, distorted through a "lens" (glass), shows brighter areas (brighter than directly lit by the same light source) and darker areas (perhaps as dark as a shadow from an opaque object, leaving just ambient light). Is the same true for the gravitational lens effect?
I imagine an observer in such a bright spot as being able to see a gravitational lensed background galaxy unusually bright, and an observer in such a dark spot as seeing very little of the same background galaxy. Does it actually work something like this? Can it be that we miss some of those background galaxies because light is mostly bended away from us?

by **neufer** » Mon Sep 21, 2009 9:01 am

http://apod.nasa.gov/apod/ap090921.html wrote:
Explanation: While imaging the cluster of galaxies Abell 370,
astronomers had noted an unusual arc to the right of "many cluster galaxies."

Since we are really observing multiple images of the same galaxy
from slightly different angles
I wonder if some clever person could make a galactic 3D image.

http://antwrp.gsfc.nasa.gov/apod/ap090823.html
http://antwrp.gsfc.nasa.gov/apod/ap080917.html
http://antwrp.gsfc.nasa.gov/apod/ap070516.html
http://antwrp.gsfc.nasa.gov/apod/ap080728.html
http://antwrp.gsfc.nasa.gov/apod/ap080210.html
http://antwrp.gsfc.nasa.gov/apod/ap070311.html
http://antwrp.gsfc.nasa.gov/apod/ap060524.html
http://antwrp.gsfc.nasa.gov/apod/ap040627.html

by **Case** » Mon Sep 21, 2009 8:57 am

http://apod.nasa.gov/apod/ap090921.html

Abell 370's gravity caused the background galaxies' light -- and others -- to spread out and come to the observer along multiple paths

Bilbo Baggins: "I'm old, Gandalf. I know I don't look it, but I'm beginning to feel it in my heart. I feel... thin. Sort of stretched, like... butter scraped over too much bread." (LotR:FotR/PJ/2001)

Starship Asterisk*

Abell 370: Galaxy Cluster Gravitational Lens (2009 Sept 21)

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