In 1934 Bulgarian born Fritz Zwicky of the California Institute of Technology recogzined that there wasn’t nearly enough visible mass in the universe to hold galaxies together and that there must be some unknown gravitational force –what we now call dark matter (simulation left). It now appears that perhaps as much as 99% of the universe is composed of Fritz Zwicky’s “dark matter.”
In other words, we live in a universe that for the most part we can’t even see. However thanks to Hubble Space Telescope, it looks as though a breakthrough has been made in our understanding of the mystery.
To explain the phenomena more precisely, matter and energy are equivalent and count as “matter” in cosmic bookkeeping. Astronomers estimate with some confidence that dark energy constitutes two-thirds of the mass of the universe, with dark matter making up almost all of the other third, while Earth, planets, stars, and interstellar dust and gas –the “bright matter”- account for less that one percent of the universe by weight.
Almost by accident astronomers using the Hubble Telescope bumped in to a ring of the supposed substance, which was apparently formed after two galaxy clusters collided with each other. Spotted unexpectedly in the galaxy cluster Cl 0024+17 by researchers from Johns Hopkins University and the Space Telescope Science Institute, the clusters lies some 5 billion light-years from Earth, and measures an impressive 2.6 million light-years across.
Dark matter and normal matter were wrenched apart by the tremendous collision of the two clusters of galaxies. Unknown in make up or where it came from, dark matter is thought to provide the universe with the extra gravity that it needs to keep from spinning out of control. The gravity exuded by stars that dwarf our own sun, apparently count for very little in the great scheme of things. The best that scientists can come up with is the belief that dark matter is a simple elementary particle found throughout the cosmos.
If you’re wondering how one finds something that doesn’t – “really” – exist, welcome to the club. It is located by looking at how the space affects the light produced by galaxies and entities behind that space. The dark matter has been detected indirectly by how it bends light, which it does with its gravity.
"It's like looking at the pebbles on the bottom of a pond with ripples on the surface. The pebbles' shapes appear to change as the ripples pass over them," according to Dr MJ Jee of Johns Hopkins.
An international team of scientists has assembled the first three-dimensional map (image above) that offers a look at the web-like large-scale distribution of dark matter in the Universe by analysing the Hubble COSMOS survey (the largest ever survey undertaken with Hubble).
This new map is equivalent to seeing a city, its suburbs and surrounding country roads in daylight for the first time. Major arteries and intersections are revealed and the variety of different neighbourhoods becomes evident.
The map provides the best evidence yet that normal matter, largely in the form of galaxies, accumulates along the densest concentrations of dark matter. The map reveals a loose network of filaments, intersecting in massive structures where clusters of galaxies are located.
Posted by Casey Kazan and Josh Hill.