This says it all:
By Floyd Wilson - Mar 27, 2015
A new study has unveiled that dark matter is more mysterious and weirder in nature than previously thought. Not only it is difficult to detect but it also makes up 85 percent of the mass of the universe. However, dark matter does not emit any radiation like stars and galaxies, which hinders its direct observation. For the new study, 72 collisions between clusters of galaxies have been analyzed by astrophysicists to detect the movement of stars, clouds of gas and signs of dark matter.
With the aid of the Hubble Space Telescope, observations were taken in visible light and were combined with X-ray images from the Chandra Observatory, NASA’s telescope which has been designed especially for the detection of X-ray emissions from very hot regions of the universe like exploded stars, galaxy clusters and matter around black holes. Information from stars was captured by the Hubble Space Telescope whereas the gas clouds were featured in the Chandra images.
Dark matter does not glow in the electromagnetic spectrum but its gravitational influence on visible matter can be felt. Warping of space-time can bend light passing near dark matter in much the same manner as a lens. Huge amounts of both ordinary and dark matter are present in galaxy clusters. Thus, collisions between systems allow the detection of the influences of dark matter on massive collections of traditional matter. The location of dark matter has been inferred by the scientists by analyzing the behavior of visible matter.
Richard Massey of Durham University stated “We like these collisions because it’s exactly what we’d do in the lab. If you want to figure out what something is made out of, you knock it, or you throw it across the room and see where the bits go.” The study revealed that regions of dark matter passed directly through one another without interacting. Stars mostly traveled through empty space and thus had little interaction with each other. However, during collisions, gas clouds came to a virtual standstill.
David Harvey from the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland commented “We know how gas and stars react to these cosmic crashes and where they emerge from the wreckage. Comparing how dark matter behaves can help us to narrow down what it actually is.” Evidence of dark matter was found in previous observations of the Bullet Cluster, which is a collision between a pair of large galaxy clusters, and according to the observation, the dark matter exhibited a few interactions, even with itself.
The existence of dark matter has been theorized since the late 1960s and the new study has provided further physical evidence supporting its presence. However, according to most of the theories, such collisions would have slowed dark matter but in the new study no such behavior was noticed, which calls for the development of a new theory about the mysterious substance.