High-energy particle
The mysterious new particle doesn’t have a clear point of origin
Over the years, scientists have unveiled the existence of quite a few intriguing particles, pushing O the entire field of physics forward with each discovery. There’s the ‘God particle’, for instance – the Higgs boson that grants all other particles their masses. There’s also the so-called ‘Oh-My-God’ particle, an unimaginably energetic cosmic ray. But now we have a new particle. It’s named the Amaterasu particle, and is fittingly extraordinary. This particle has an energy level a million times greater than what can be generated in even humanity’s most powerful particle accelerators. It appears to have fallen to Earth in a shower of other, less energetic particles. Like the ‘Oh-My-God’ particle, these bits come from faraway regions of space and are known as cosmic rays.
The particle has been dubbed ‘Amaterasu’ after Amaterasu Ōmikami, the goddess of the Sun and the universe in Japanese mythology. And just as its namesake is shrouded in mystery, so too is the particle. Its discoverers, including Osaka Metropolitan University researcher Toshihiro Fujii, don’t know where the particle came from, or indeed what it is. They also still aren’t sure what kind of violent and powerful process could have given rise to something as energetic as Amaterasu. “This is the most energetic charged particle ever detected by the Telescope Array experiment,” Fujii said. The hope is that, just as Amaterasu is credited with the creation of Japan according to the Shinto tradition, the Amaterasu particle can help create an entirely new branch of high-energy astrophysics.
High-energy cosmic rays are extremely rare to begin with, but Fujii said the Amaterasu particle has an energy level not seen in a staggering 30 years of cosmic ray detections. In fact, when the researchers spotted Amaterasu with the Telescope Array experiment – involving 507 detectors spread across 270 square miles (699 square kilometres) of the high desert of Millard County, Utah – they initially thought the detection must be some kind of mistake. “I thought it would be my mistake or bug, and then after checking the details of the event, I was excited to find it was not an error,” Fujii said.
First spotted by the Telescope Array experiment on 27 May 2021, the Amaterasu particle exhibits an energy of 224 exaelectron-volts (EeV). For contrast, one EeV is equivalent to 1018 electron-volts. This puts Amaterasu on a similar energy level to the
