Dark Matter

Wikipedia gives the following information about dark matter.

In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy.
Dark matter is believed to constitute 83% of the matter in the universe. Dark matter was postulated by Fritz Zwicky in 1934 to account for evidence of "missing mass" in the orbital velocities of galaxies in clusters. Subsequently, other observations have indicated the presence of dark matter in the universe; these observations include the rotational speeds of galaxies, gravitational lensing of background objects by galaxy clusters such as the Bullet Cluster, and the temperature distribution of hot gas in galaxies and clusters of galaxies.

Let's look at recent scientific research about dark matter.

Scientists will need further analysis to discern whether dark matter caused any of the COUPP-60 experiment's first bubbles at the SNOLAB underground science laboratory in Ontario, Canada. Dark matter accounts for nearly 90 percent of all matter in the universe, yet it is invisible to telescopes.

The AMS results are based on some 25 billion recorded events, including 400,000 positrons with energies between 0.5 GeV and 350 GeV, recorded over a year and a half. This represents the largest collection of antimatter particles recorded in space. The positron fraction increases from 10 GeV to 250 GeV, with the data showing the slope of the increase reducing by an order of magnitude over the range 20-250 GeV. The data also show no significant variation over time, or any preferred incoming direction. These results are consistent with the positrons originating from the annihilation of dark matter particles in space, but not yet sufficiently conclusive to rule out other explanations.

This fall, the Kavli Institute for Cosmological Physics at the University of Chicago and the National Academy of Sciences organized a colloquium that brought together more than 100 cosmologists, particle physicists and observational astrophysicists -- three fields now united in the hunt to determine what is dark matter. Their goal: to take stock of the latest theories and findings about dark matter, assess just how close we are to detecting it and spark cross-disciplinary discussions and collaborations aimed at resolving the dark matter puzzle.

Lawrence Livermore National Laboratory researchers are making key contributions to a physics experiment that will look for one of nature's most elusive particles, "dark matter," using a tank nearly a mile underground beneath the Black Hills of South Dakota.

These conclusions are drawn based upon the precise distances to celestial objects in the Galaxy and their proper motions, a technical term to describe the stars' change in position. The International Astronomical Union has endorsed V0=220km/s; this value was announced in 1986. When the V0 value derived from this research is applied, the mass of dark matter in the galaxy is about 20% larger than what has been considered so far.

Our measurements contradict a basic prediction about the structure of cold dark matter in dwarf galaxies. Unless or until theorists can modify that prediction, cold dark matter is inconsistent with our observational data.

Brown University physicists have set the strongest limit for the mass of dark matter, the mysterious particles believed to make up nearly a quarter of the universe. The researchers report in Physical Review Letters that dark matter must have a mass greater than 40 giga-electron volts. The distinction is important because it casts doubt on recent results from underground experiments that have reported detecting dark matter.

There's more to the cosmos than meets the eye. About 80 percent of the matter in the universe is invisible to telescopes, yet its gravitational influence is manifest in the orbital speeds of stars around galaxies and in the motions of clusters of galaxies. Yet, despite decades of effort, no one knows what this "dark matter" really is. Many scientists think it's likely that the mystery will be solved with the discovery of new kinds of subatomic particles, types necessarily different from those composing atoms of the ordinary matter all around us. The search to detect and identify these particles is underway in experiments both around the globe and above it.

The most accurate study so far of the motions of stars in the Milky Way has found no evidence for dark matter in a large volume around the Sun. According to widely accepted theories, the solar neighbourhood was expected to be filled with dark matter, a mysterious invisible substance that can only be detected indirectly by the gravitational force it exerts. But a new study by a team of astronomers in Chile has found that these theories just do not fit the observational facts. This may mean that attempts to directly detect dark matter particles on Earth are unlikely to be successful.

Astronomers from the University of Bonn in Germany have discovered a vast structure of satellite galaxies and clusters of stars surrounding our Galaxy, stretching out across a million light years. The work challenges the existence of dark matter, part of the standard model for the evolution of the universe.