by JENNIFER CHU
The starboard truss of the International Space Station while Space Shuttle Endeavour docked with the station. The newly installed Alpha Magnetic Spectrometer (AMS) is visible at center left. PHOTO/NASA
The MIT group leads an international collaboration of scientists that analyzed two and a half years’ worth of data taken by the Alpha Magnetic Spectrometer (AMS)—a large particle detector mounted on the exterior of the International Space Station—that captures incoming cosmic rays from all over the galaxy.
Among 41 billion cosmic ray events—instances of cosmic particles entering the detector—the researchers identified 10 million electrons and positrons, stable antiparticles of electrons. Positrons can exist in relatively small numbers within the cosmic ray flux.
An excess of these particles has been observed by previous experiments—suggesting that they may not originate from cosmic rays, but come instead from a new source. In 2013, the AMS collaboration, for the first time, accurately measured the onset of this excess.
The new AMS results may ultimately help scientists narrow in on the origin and features of dark matter—whose collisions may give rise to positrons.
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