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The uncertainty of science: A Chinese space probe designed to measure cosmic rays has detected a pattern that could be evidence of the existence of dark matter.
Researchers launched the spacecraft from the Jiuquan Satellite Launch Center in the Gobi Desert, about 1600 kilometers west of Beijing, in December 2015. Its primary instrument—a stack of thin, crisscrossed detector strips—is tuned to observe the incoming direction, energy, and electric charge of the particles that make up cosmic rays, particularly electrons and positrons, the antimatter counterparts of electrons. Cosmic rays emanate from conventional astrophysical objects, like exploding supernovae in the galaxy. But if dark matter consists of WIMPs, these would occasionally annihilate each other and create electron-positron pairs, which might be detected as an excess over the expected abundance of particles from conventional objects.
In its first 530 days of scientific observations, DAMPE detected 1.5 million cosmic ray electrons and positrons above a certain energy threshold. When researchers plot of the number of particles against their energy, they’d expect to see a smooth curve. But previous experiments have hinted at an anomalous break in the curve. Now, DAMPE has confirmed that deviation. “It may be evidence of dark matter,” but the break in the curve “may be from some other cosmic ray source,” says astrophysicist Chang Jin, who leads the collaboration at the Chinese Academy of Science’s (CAS’s) Purple Mountain Observatory (PMO) in Nanjing. [emphasis mine]
I must emphasize the large uncertainty here. They have not detected dark matter. Not even close. What they have detected is a pattern in how the spacecraft is detecting cosmic rays that was predicted by the existence of dark matter. That pattern however could have other causes, and the consistent failure of other efforts to directly find dark matter strengthens the possibility that this break is caused by those other causes.