Dark Matter: Hints Of Elusive Substance Found

By Thomas Moore, Health and Science Correspondent

Scientists have revealed the most convincing physical evidence yet that dark matter, a mysterious and elusive component of the universe, really does exist.

Dark matter makes up more than a quarter of the universe, but cannot be seen with telescopes.

Physicists have so far only seen clues that it exists from its gravitational effects on visible galaxies.

The Endeavour took the AMS into space

But now a machine spinning around the globe aboard the International Space Station has provided the first glimpse of what could be dark matter.

The $2bn (£1.3bn) detector has for the first time spotted "fallout" that could come from dark matter colliding with itself somewhere in space.

The process is called "annihilation" and creates positrons, the positively-charged mirror image of electrons.

Researchers from Nasa and Cern say the particles detected by the Alpha Magnetic Spectrometer (AMS) could come from a dying star called a pulsar.

But they were seen over a period of time and not from a single source, suggesting they originate from dark matter.

"There is no question we are going to solve this problem," said project leader Professor Samuel Ting from the Massachusetts Institute of Technology.

"Over the coming months AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin."

The seven-ton AMS has a massive magnet at its heart that generates a magnetic field 3,000 times stronger than the Earth's.

The magnet bends particles from cosmic rays onto a series of detectors.

This Hubble telescope image is believed to provide evidence of dark matter

In the first 18 months of the experiment - the most expensive one ever carried out in space - the AMS has detected 30 billion particles. More than 400,000 of them were positrons.

Visible matter makes up less than 5% of the universe. Scientists believe that dark matter could help them understand the universe's origin and evolution.

The AMS, built by a team of 16 countries, arrived on the International Space Station aboard the space shuttle Endeavour's final flight in May 2011.

Since then, it has been collecting data from millions of light years beyond our galaxy, the Milky Way.

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