Monday, February 06, 2006
... and there was light (matter)
| By Jonathan Amos BBC News science reporter |
This strange material that dominates the Universe but which is invisible to current telescope technology is one of the great enigmas of modern science.
That it exists is one of the few things on which researchers have been certain. But now an Institute of Astronomy, Cambridge, team has at last been able to place limits on how it is packed in space and measure its "temperature".
"It's the first clue of what this stuff might be," said Professor Gerry Gilmore. "For the first time ever, we're actually dealing with its physics," he told the BBC News website........
........'Magic volume'
Astronomers cannot detect dark matter directly because it emits no light or radiation. Its presence, though, can be inferred from the way galaxies rotate: their stars move so fast they would fly apart if they were not being held together by the gravitational attraction of some unseen material.
Such observations have established that dark matter makes up more than 95% of all cosmic material. Now, the Cambridge team has provided new information with its detailed study of 12 dwarf galaxies that skirt the edge of our own Milky Way.
Using the biggest telescopes in the world, including the Very Large Telescope facility in Chile, the group has made detailed 3D maps of the galaxies, using the movement of their stars to "trace" the impression of the dark matter among them and weigh it very precisely.
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....
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| | If this 'temperature' for the dark matter is correct, then it has huge implications for direct searches for these mysterious particles Prof Bob Nichol Institute of Cosmology and Gravitation, Portsmouth |
"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."...
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