Close to the Edge
Observatory Report - Subject Cosmology- The Universe
Itis one of the biggest mysteries in science which has baffled scholars for more than 75 years, but now a team of cosmologists believes it has found a way of discovering what the universe is made of.
About 85 per cent is neither stars nor planets but some form of mysterious matter. It cannot be seen or detected by conventional scientific instruments, which is why the precise nature of this "dark matter" has eluded the finest minds in science.
Now cosmologists believe the problem will be solved within two years, thanks to the results of a vast computer simulation of the Milky Way galaxy that has provided the first cosmic map of where dark matter can be found and how find it.
The simulation predicts that there are regions near the centre of the Milky Way where dark matter will emit a glow of powerful gamma radiation that could be detected by a Nasa satellite launched this year specifically to search for this type of cosmic ray.
Powerful supercomputers which have modelled all known aspects of dark matter predict that a set of hitherto undiscovered sub-atomic particles must account for the 85 per cent of the matter in the universe that is missing from view.
The simulation predicts that in regions near the centre of our galaxy these sub-atomic particles become tightly packed so they collide, and in the process emit a gamma-ray glow that should be detectable by the Fermi telescope, the latest satellite observatory to be launched by Nasa.
"We have provided a detailed blueprint for Fermi to find dark matter," said Professor Carlos Frenk of Durham University. "It shows where to look and what to look for. This is a blueprint for solving one of the greatest mysteries in science, which is what the universe is made of. The search for dark matter has dominated cosmology for decades. It may soon come to an end. I think within a year, or two years maximum. Now we've told them what to look for, all they need to do is to just go and do it."
The simulation, published in the journal Nature, took 3.5 million hours of computer processing time to complete. It revealed that dark matter would form structures around galaxies and that these "halos" should be detectable by Fermi because of the gamma-ray glow they emit.
These dark-matter halos are invisible to all other scientific instruments even though they are more than a trillion times as massive as the sun and form the basic unit of a vast structural network that interweaves all known galaxies in the universe.
"These calculations finally allow us to 'see' what the dark matter distribution should look like near the sun where we might stand a chance of detecting it," said Professor Simon White, director of the Max Planck Institute for Astrophysics in Garching, Germany.
There are two broadly competing theories about the nature of dark matter. One is that it is composed of large, planet-sized objects, called Machos, and the others made of sub-atomic particles, known as Wimps. Most cosmologists are edging towards the latter.
Theoretical physicists have proposed that there is a class of sub-atomic particles in perfect symmetry to existing, known particles, but which are so weakly interacting that they cannot be detected with existing instruments.
But the Fermi telescope may now detect the gamma radiation emitted from these particles, and the Large Hadron Collider experiment in Geneva may actually create these symmetrical particles when it becomes fully operational next year.
Professor Frenk added: "We will soon know exactly what that dark matter is, and the LHC will look for it as well. I'm hoping it will actually make dark matter, or something similar."
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