A Chinese Dark Matter Satellite Has Found An Interesting Signal

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A Chinese dark matter satellite has discovered something interesting that may be related to dark matter particles. As of yet, we've never directly detected such particles.

The satellite is called the Dark Matter Particle Explorer (DAMPE). It’s nicknamed Wukong, which translates as “Monkey King”, and was launched in December 2015.

The satellite is designed to look for the decay signal of a hypothetical dark matter candidate called a weakly interacting massive particle (WIMP). It looks for the decay of WIMPs, which are expected to annihilate each other occasionally and produce pairs of electrons and positrons.

The first results from the mission were published today in Nature. In its first 530 days of scientific observations, it detected 1.5 million cosmic ray electrons and positrons above 25 gigaelectronvolts (GeV). And it has found 3.5 billion cosmic rays with energies above 100 trillion electronvolts (TeV).

In its total life, about five years, the satellite is expected to record 10 billion cosmic rays events.

What’s particularly interesting about these latest findings, though, is that the satellite observed a “spectral break” in the number of electrons and positrons from cosmic rays at the 900 billion electronvolt mark. And no one is entirely sure why that break is there.

One possibility is that dark matter particles are responsible for the break. But cosmic rays from pulsars or supernovae could also be the cause, so scientists aren’t jumping to any conclusions just yet.

“It may be evidence of dark matter,” astrophysicist Chang Jin, project leader from the Chinese Academy of Science’s (CAS’s) Purple Mountain Observatory (PMO) in Nanjing, told Science Magazine. But he added it  “may be from some other cosmic ray source.”

DAMPE is a collaboration between more than a hundred scientists from China, Switzerland, and Italy. The satellite orbits at a height of about 500 kilometers (310 miles) above Earth.

"Together with data from the cosmic microwave background experiments, high energy gamma-ray measurements, and other astronomical telescopes, the DAMPE data may help to ultimately clarify the connection between the positron anomaly and the annihilation or decay of particle dark matter," Fan Yizhong, the deputy chief designer of DAMPE's scientific application system, said in a statement.

The spectral break mentioned above has been spotted before, by a telescope array in Namibia called HESS and the CALorimetric Electron Telescope on the International Space Station. These latest findings, however, could help us narrow down exactly what’s going on. It brings us a step closer, though, to making the first-ever direct detection of dark matter.

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