The universe is mostly made up of dark matter – a non-luminous material that scientists cannot directly observe. It’s five times more abundant than ordinary matter, which makes it one of the greatest scientific mysteries.
Scientists have been trying to crack it for decades, and Wukong’s recent measurement of energy distribution of cosmic ray electrons with energies as high as 5 tera electron Volts may shed light on this.
Researcher said this data might suggest that dark matter is not necessarily “dark”, meaning that with more data, they might be one step closer to discovering what it really is.
The annihilation and decay of dark matter particles in the Milky Way and nearby galaxies is expected to leave relics in high-energy cosmic rays and gamma rays. By observing these cosmic and gamma rays when they propagate to Earth’s neighborhood, scientists can, in turn, determine their properties and origins.
“Dark matter is not visible, but when it annihilates or decays, it produces ordinary particles that can be detected and studied,” explained Chang Jin, deputy director of Purple Mountain Observatory at the Chinese Academy of Sciences. “Wukong is able to detect, and most importantly, distinguish different particles, which can help us study them.”
“The explorer weighs 1.4 tons and the heaviest compartment is the BGO crystal calorimeter, used to detect energy of particles,” Wu Ji, director of the National Space Science Center and the Chinese Academy of Sciences, said. “Our team has developed the world’s longest crystal bars, which we’ve installed inside Wukong to expand the area of data collection.”
During the first 17 months of exploration, Wukong was able to detect 1.5 million cosmic ray electrons out of a total of 25 billion events, with unprecedented low particle background contamination and high-energy resolution.
Since it’s launch in December 2015, Wukong has recorded about 3.5 billion cosmic ray events, with a maximum event energy exceeding 100 trillion electron volts.
The satellite is expected to record more than 10 billion cosmic ray events in the next few years. By collecting more data, scientists are hoping they will gain new insight into the nature of dark matter.