Is dark matter responsible for the unexplained antimatter rain hitting Earth?
In short: For over fifteen years, scientists have tracked an unexpected flood of positrons striking our atmosphere. While many suspected nearby spinning stars were the culprits, new evidence suggests a much more exotic origin: the mysterious substance known as dark matter.
The mystery began in 2008, when the PAMELA detector identified a significant overabundance of high-energy positrons—the antimatter counterparts to electrons—hitting Earth's atmosphere. These findings, later confirmed by the Fermi Gamma-ray Space Telescope and the Alpha Magnetic Spectrometer (AMS-02) on the International Space Station, revealed that the number of high-energy protons was roughly three times greater than standard models predicted. When these positrons encounter normal matter, they annihilate, releasing energetic gamma rays.
For decades, the leading theory was that pulsars—the rapidly spinning remnants of massive stars—acted as cosmic particle accelerators. Specifically, researchers looked toward two nearby pulsars, Geminga and PSR B0656+14 (also known as Monogem), which are less than a thousand light-years away. Observations from the High Altitude Water Cherenkov (HAWC) observatory in Mexico, which uses 300 water tanks to detect particle showers, have tracked high-energy gamma rays from these sources.
However, a recent study published in the journal Science has complicated this narrative. Rubén López Coto, leading the Max Planck Institute for Nuclear Physics research, suggests that the observed surplus of positrons might not be fully explained by these dual pulsars. This has led some researchers to propose that interactions involving dark matter—which is estimated to comprise roughly five-sixths of all matter in the universe—could be the true source. This remains a subject of intense debate, as some physicists, such as Dan Hooper of Fermi National Accelerator Laboratory, still believe pulsars could dominate the local positron excess.
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Sources
- Summary by Intellect · source: We Finally Found Out What Is Bombarding the Earth with Antimatter
- Also: Through a Gas, Darkly: Scientists Trace the Origins of Earth
- Also: Mysterious Particles Are Slamming Into Earth—But Why?
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