Until now, the only thing scientists have known for certain about dark matter is that it exists. Baryonic matter, or dark matter, cannot be measured directly because it emits no light or radiation. For the first time, however, a team of scientists from the Institute of Astronomy, University of Cambridge, was recently able to measure some of the physical characteristics of the stuff.

With the aid of 7,000 separate measurements, the researchers have been able to establish that the galaxies contain about 400 times the amount of dark matter as they do normal matter.

"The distribution of dark matter bears no relationship to anything you will have read in the literature up to now," explained Professor [Gerry] Gilmore. "It comes in a 'magic volume' which happens to correspond to an amount which is 30 million times the mass of the Sun."

"It looks like you cannot ever pack it smaller than about 300 parsecs – 1,000 light-years; this stuff will not let you. That tells you a speed actually – about 9km/s – at which the dark matter particles are moving because they are moving too fast to be compressed into a smaller scale. These are the first properties other than existence that we've been able [to] determine."

The speed is a big surprise. Current theory had predicted dark matter particles would be extremely cold, moving at a few millimetres per second; but these observations prove the particles must actually be quite warm (in cosmic terms) at 10,000 degrees.

The most likely candidate for dark matter material is the so-called weakly interacting massive particle, or Wimp.

Hmmm . . . WIMPs in space. OK.

I don't pretend to understand any of this. I just find it fascinating.

More information on dark matter is posted at the BBC Science site. Besides WIMPs in space, there are also MACHOs, Massive Astronomical Compact Halo Objects.