Physicists have announced the results of the first data from the Alpha Magnetic Spectrometer (AMS), which is based on the International Space Station, revealing that the instrument may have detected the first hints of dark matter in the universe.
Dark matter remains one of the biggest mysteries in physics. It can be observed indirectly through its interaction with visible matter but has yet to be directly detected.
The US$2bn AMS instrument has been based at the International Space Station since 2011, when it was carried into orbit during the last voyage of the space shuttle Endeavour. The instrument was installed on the station’s truss structure where it has been tracking incoming charged particles, such as protons, electrons and antimatter particles, such as positrons, ever since.
The idea for the AMS project began in 1984, when it was conceived by Nobel Laureate Prof Samuel Ting, a physicist from MIT.
Dark matter enigma
Speaking at CERN in Geneva, Switzerland, yesterday, Ting announced the first results from the AMS instrument’s search for dark matter. Ting said he expects to have a more definitive answer on the existence of dark matter in the coming months.
"As the most precise measurement of the cosmic ray positron flux to date, these results show clearly the power and capabilities of the AMS detector," he said. "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."
According to CERN, an excess of antimatter within the cosmic ray flux was first observed around two decades ago. Yet, the origin of this excess antimatter remains unexplained.
One possibility posited by the theory of supersymmetry is that positrons could be produced when two particles of dark matter collide and annihilate.
Ting said the findings from AMS could point to dark matter collisions. However, he said there was the possibility that the positrons could alternatively originate from pulsars – highly magnetised, rotating neutron stars.
"AMS is the first experiment to measure to 1pc accuracy in space. It is this level of precision that will allow us to tell whether our current positron observation has a dark matter or pulsar origin," said Ting.
According to NASA, about 70pc of the universe is dark energy, while dark matter makes up the remaining 25pc. The remainder, including everything on Earth and everything that’s ever been observed using scientific instruments, makes up the remaining 5pc, termed ‘normal matter’.
Cosmic rays are charged high-energy particles that permeate space. The AMS experiment is designed to study them before they have a chance to interact with the Earth’s atmosphere.
Searches for dark matter are also carried out at the Large Hadron Collider at CERN.
Rolf Heuer, the director-general at CERN, said the AMS result is a great example of the complementary experiments being carried out at CERN and in space.
"Working in tandem, I think we can be confident of a resolution to the dark matter enigma sometime in the next few years," said Heuer.
The Large Hadron Collider is currently in shutdown mode for upgrades to increase its beam energy. It is set to re-open in early 2015.
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