Dark Matter & Dark Energy

If you are lucky enough to live away from any light pollution or have travelled to remote locations, you may have spent some time staring in awe at the countless dots of light adorning our heavenly ceiling. So, it may come as a bit of a shock that you are only seeing less than 4 percent of what is actually "out there".

By observing how galaxies and stars are moving through space, researchers have come to the conclusion that there must be something keeping them in their orbits that we just cannot see; even with modern scientific instruments. This invisible glue has been named dark matter and our field guide to lead us through this hidden landscape was Dr Carlo Nicola Colacino from Birmingham University.

In 1933, a Swiss astrophysicist called Fritz Zwicky was studying a huge cluster of over a thousand galaxies known as the Coma Cluster. By focussing on the motions of the outlying galaxies he came to a figure for the total mass of the Cluster. However, this didnīt tally with the estimate for the total mass calculated according to the number of galaxies in the Cluster and their brightness. The discrepancy was not small, either: the two methods were out by a factor of 400! Hence, the "missing mass problem" was born.

It is thought that a very small amount of the missing mass could be made up of baryons. We come across this type of matter in our everyday life, including our own bodies. This variety of dark matter has the rather obvious title of baryonic dark matter and consists of any object that gives off little or no light. Examples are huge clouds of non-luminous gas, dwarf stars, neutron stars and black holes.

However, this baryonic dark matter is only the tip of the iceberg, so to speak. One team of scientists is hoping that they may have the answer to the rest of the missing matter in the guise of a new particle called the neutralino. This theoretical particle rarely interacts with normal matter but they are hoping to spot it over a kilometre down in the deepest mine in Europe. The team has taken advantage of the commercial mining of potash in Boulby Mine in North Yorkshire to set up special detectors but so far they have not seen the elusive particle.

At present, researchers seem to be having more luck by studying galaxies. A team from the Institute of Astronomy in Cambridge has come up with some interesting conclusions about dark matter by observing the motions of 12 dwarf galaxies orbiting the Milky Way. They have found that each galaxy contains 400 times the amount of dark matter as normal matter and the dark matterīs average temperature and speed mean it is relatively hot in cosmic terms. These latest findings will perhaps help the astrophysicists in Boulby Mine close in on these dark particles.