More than three years ago, scientists working with NASA's Chandra X-Ray Observatory announced that they have found direct evidence that dark matter exists in the universe. Dark matter is one of the holy grails of astronomy since little is known about it though theories say it accounts for 90 per cent of the matter of the Universe. In this image, a purple haze shows dark matter flanking the "Bullet Cluster." NEWSCOM/FILE
In this image, the Bullet Cluster is made of two colliding groups of galaxies. NEWSCOM/FILE
In this image, the Hubble Space Telescope was used to observe how the Bullet Cluster bent light coming from background stars. NEWSCOM/FILE
The NGC 2300 group of galaxies contains a large reservoir of million-degree gas glowing in X-rays. A false-color X-ray image of the hot gas is superimposed here on an optical picture of the galaxy group. Gravity from the galaxies alone is not enough to keep the gas in its place. There must be large quantities of dark matter whose gravity is preventing the gas from escaping. NEWSCOM/FILE
Dark Matter Astronomers using NASA's Hubble Space Telescope have discovered a ghostly ring of dark matter that formed long ago during a titanic collision between two massive galaxy clusters. The ring's discovery is among the strongest evidence yet that dark matter exists. NEWSCOM/FILE
CDMS Dark Matter musical detector. Members of the research group, Cryogenic Dark Matter Search, have registered what they believe may be the first bits of subatomic particles known as dark matter. Scientists cooled germanium and silicon to nearly absolute zero and over the course of two years the supposed dark matter registered as pulses of heat deposited in the cooled materials. If the particles are confirmed to be dark matter it would mean that after more than 50 years of research physicists are finally closing in on the invisible material that constitutes 25% of the universe. NEWSCOM/FILE
Gravitational lensing image of galaxies (yellow to red) and halos from clumped dark matter (blue). PRIYA NATARAJAN/YALE UNIVERSITY
SNAP - the SuperNova Acceleration Probe - is a proposed space observatory designed to measure the expansion of the Universe and to determine the nature of the mysterious Dark Energy that is accelerating this expansion. SNAP is being proposed as part of the Joint Dark Energy Mission (JDEM), which is a cooperative venture between NASA and the U.S. Department of Energy. If selected it will be launched before 2020. This is an artist's conception of the SuperNova/Acceleration Probe (SNAP) satellite, one of three concepts contending for the DOE-NASA Joint Dark Energy Mission. COURTESY: Lawrence Berkeley National Laboratory.