China released the first batch of gamma photon data obtained by the Dark
Matter Particle Explorer satellite-based telescope on Tuesday, allowing
scientists to improve their hunt for elusive dark matter.
Dark matter is a type of substance that cannot be directly observed but is
believed to account for around 80 percent of the mass of the universe. Gamma
photons are the most energetic particles of light in the electromagnetic
spectrum.
The telescope, also known as Wukong or Monkey King, has collected data on
around 10.7 billion high-energy cosmic rays since its launch in 2015,
according to the National Space Science Data Center and the Purple Mountain
Observatory of the Chinese Academy of Sciences.
The data released was recorded from Jan 1, 2016 to Dec 31, 2018, and
included 99,864 gamma photons. More data sets will be released in the
future, the two institutions said.
The missions of the telescope include studying properties of dark matter by
taking a closer look at high-energy gamma rays and electrons, as well as
examining the possible origins and acceleration mechanism of cosmic rays,
high-energy protons and atomic nuclei that move through space at nearly the
speed of light.
Chang Jin, a CAS academician and chief scientist of the Wukong telescope,
said in a public lecture that the high-energy cosmic rays may be generated
in the annihilation or decay of dark matter.
Since gamma photons do not carry an electric charge like protons and
electrons, they are less likely to be affected by the magnetic field of
other celestial bodies and events, hence they may carry more accurate
information about dark matter and the origins of cosmic rays, he said.
In 2019, an international team of researchers studying data collected by the
Wukong telescope measured cosmic ray protons up to 100 trillion electron
volts with high precision for the first time, according to a study published
in the journal Science Advances.
Before the launch of Wukong, balloon experiments could only directly measure
cosmic rays with energies up to 2 trillion electron volts, while
ground-based telescope arrays could indirectly measure such particles with
energies up to about 5 trillion electron volts.
One of the biggest and strangest discoveries made by Wukong is that there is
a "spectral break", a drop in the number of cosmic ray electrons and
positrons, at about 900 billion electron volts, and nobody knows why this
dip exists, according to a study published in the
journal Nature
in 2017.
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Physics