Nasa image of the day 16/5

[Jamie]

2007 May 16

Dark Matter Ring Modeled around Galaxy Cluster CL0024+17

Credit: NASA, ESA, M. J. Jee & H. Ford et al. (Johns Hopkins U.)

Explanation: How do we know that dark matter isn't just normal matter exhibiting strange gravity? A new observation of gravitationally magnified faint galaxies far in the distance behind a massive cluster of galaxies is shedding new dark on the subject. The above detailed image from the Hubble Space Telescope indicates that a huge ring of dark matter likely exists surrounding the center of CL0024+17 that has no normal matter counterpart. What is visible in the above image, first and foremost, are many spectacular galaxies that are part of CL0024+17 itself, typically appearing tan in color. Next, a close inspection of the cluster center shows several unusual and repeated galaxy shapes, typically more blue. These are multiple images of a few distant galaxies, showing that the cluster is a strong gravitational lens. It is the relatively weak distortions of the many distant faint blue galaxies all over the image, however, that indicates the existence of the dark matter ring. The computationally modeled dark matter ring spans about five million light years and been digitally superimposed to the image in diffuse blue. A hypothesis for the formation of the huge dark matter ring holds that it is a transient feature formed when galaxy cluster CL0024+17 collided with another cluster of galaxies about one billion years ago, leaving a ring similar to when a rock is thrown in a pond.

[Kaptain Klevtsov]

Interesting stuff. Now I know not to buy a cheap gravitational lens, everything looks bluish through it.

Captain Chaos

[barkis]

This dark matter theory has got me totally perplexed. Is there a book anywhere that explains why it has recently exploded onto the scene, and why it is being thrust into the equation to compensate for the missing matter in the universe. Where does this leave the string theory, or has that too been conveniently woven into the tapestry that is endlessly being created.

Now, I apologize if what I have said sounds like a load of garbage, but I am no physicist, and that is an understatement.

I would just like to sit down with a well written account of where we are at present with it all, and it would have to be in a very basic language, or is that asking too much.

Ron.

[GordonCopestake]

MOND is gone baby!

[themos]

It's not recent.

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit6/dark.html

[themos]

String theory is accused of being "not even wrong", in the sense that it makes no firm predictions. If you hear about strings and cosmology, be careful in case people are talking of "cosmic strings". They are just string-like configurations of fields we know about and have macroscopic (indeed, cosmic) dimensions and they have nothing to do with the fundamental strings of superstring theory and the like.