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Galaxy Cluster Abell 1689 Magnifies the Dark Universe

Explanation: What's the matter with this cluster of galaxies? To find out what forms matter takes in the Abell 1689 cluster requires not only deep images from telescopes like the Hubble Space Telescope, but detailed computer modeling as well. To start, almost every fuzzy yellow patch in the above image is an entire galaxy. A close inspection, however, shows that many background galaxies are strangely magnified and distorted into long curving arcs by the gravitational lens deflections of the cluster. Computer analyses of the placement and smoothness of these arcs indicate that in addition to the matter in the galaxies you can see, the cluster must also contain a significant amount of dark matter such as the model digitally superposed in purple. Now Abell 1689 remains enigmatic because the arcs are so numerous and diverse that no single dark matter model has emerged that can explain them all and still remain consistent with dark matter models needed to constrain their motion. Still, the detailed information available from clusters of galaxies like Abell 1689 gives hope that one day full solutions will be found that will not only fully reveal the dark matter in clusters, but also reveal the amounts of dark energy in the universe needed to lie along the line of sight to the distant arcs.

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A plethora of galaxies.
A fantastic image.
A heavenly piñatas market.

That means a plethora?

Animation of lensing! http://www.youtube.com/watch?v=2-My9CChyBw

Yeah, that's a very cool little video!

And this is a very cool APOD. If I ever learn anything about astronomy, enough to make presentations about it, this is an image I'd include in such presentations; SO full of topics to talk about!

(I had to build a distance learning class recently for a grad school assignment and chose to create a class for kids on skywatching, which included meterology, atmospheric optics, and astronomy, so presenting stuff has been on my mind.)

Change DATE above Image from August 22 to 24...

I suppose it's semantics, but for me that video demonstrates distortion by direct viewing across the event horizon of a very, very steep gravity well, a black hole. Gravity lensing causes more angular distortion and apparent relocation of the original object, and occurs with extremely large , but extremely diffuse masses, like concentrations of dark matter, but it's all relative!

John

Using similar computer techniques, wouldn't it be possible to reconstruct the "smeared" galaxy images into a more visually coherent image?
Using gravity as a kind of "intergalactic Barlow lens" might help us to better understand the structures of galaxy formation in the early universe.

Thanks for the link to the video, Orin!

Ann

Ann wrote:Thanks for the link to the video, Orin!

Ann

Thanks Ann; but I just copied it from a link in the explanation of today's APOD! Sometimes those links are easy to overlook. It kind of reminded me of taking a strong magnifying glass over a picture rather quickly. Maybe that's why it is called lensing! It's too bad gravitational lensing distorts distant galaxies so bad.

Hi,
At the upper right of the Abell 1689 image (yellow box) I noted two galaxies with what may look like supernovae. I know it seems unlikely, are those just intervening stars or what?

Of course, if John Moffat is right, there's no dark matter at all, just a modified law of gravity ...

Warhorse wrote:Of course, if John Moffat is right, there's no dark matter at all, just a modified law of gravity ...

Of course, if John Moffat is right, we have a lot more to worry about than dark matter, such as c not being constant ...

With no more than intuition to go on, I've been thinking for a long time that inventing something we can't see nor detect directly is a bad idea to explain where observation diverges from theory.

I guess that puts me in the camp that believes that some part of the math is wrong somewhere...

Food for thought: We're peering back in time, to when the Universe was younger, more dense, and expanding at a different rate than now... Isn't it possible the laws of physics are aging?

-Noel

NoelC wrote:With no more than intuition to go on, I've been thinking for a long time that inventing something we can't see nor detect directly is a bad idea to explain where observation diverges from theory.

Almost everything we observe is observed indirectly. People tend to be so focused on what they can see with light that they don't trust anything else. I guess it's because we depend so heavily on our eyes. Personally, it doesn't much matter to me. The observational evidence seems overwhelming for the existence of dark matter, and it makes cosmological theory work better. Hard to resist that combo!