What you see here in blue is an enormous cloud of Dark Matter surrounding a cluster of galaxies. The white dots are not stars, but galaxies! The Dark Matter distribution was reconstructed from distortions of light rays from background galaxies by the gravitational effects of the intervening Dark Matter.
Dark Matter is everywhere! It fills the large spaces between galaxies and concentrates around them in gigantic clouds. Although invisible, it reveals its presence by its immense gravitational pull.
The quest for the mysterious missing mass of the Universe has become one of the big challenges of today's particle physics and cosmology. Astronomical observations show that only 1% of the matter of the Universe is luminous. So where is the remaining part? Are faint brown dwarfs, Jupiter like or large unknown non-luminous objects the culprits? Or is the missing matter hidden in clouds of a new form of up to now not identified particles?
In fact there is now convincing evidence that 85% of all gravitationally observable matter in the Universe is of a new exotic kind, different from the "ordinary" matter surrounding us with its protons, neutrons and electrons. This so-called Cold Dark Matter (CDM) is thought to consist of "neutralinos" neutral particles, about hundred to thousand times heavier than a proton and which interact extremely weakly with each other and ordinary matter. Neutralinos were created during the Big Bang, and we believe that they surround most galaxies, and also our Milky Way in gigantic clouds.
More about neutralino dark matter