We may have finally solved an ultra-high-energy cosmic ray puzzle

We focus on the real composition of the rarest and most energetic cosmic rays – which could help reveal their unknown origins.

The universe constantly doubts us about particles, explains Brian Clark at the University of Maryland. The most energetic of them, called ultra-elevated cosmic rays, have more energy than even accelerated particles in collides. They are also rare – researchers do not know what produces them or where they come from. Even the particles that invent them were an unresolved question. From now on, Clark and his colleagues have determined their composition using data collected by the Neutrinos Icecube detector in Antarctica.

Previous detections of ultra -high energy cosmic rays – by the Pierre Auger observatory in Argentina and the network of UTAH telescopes – do not agree that these rays consist mainly of protons or if other particles are also in the mixture, explains Clark. Icecube data offer a certain resolution: it suggests that protons represent only 70% of ultra-high energy cosmic rays, while the rest is made of heavy ions such as iron.

The Maximilian Meier team member at the University of Chiba in Japan claims that ICecube data is complementary to other measures, which directly detect cosmic rays. On the other hand, the Icecube mainly detects the particles called neutrinos, which are by-products of collisions between the energy cosmic rays and the photons left by the Big Bang. Neutrinos themselves are difficult to detect and simulate on a computer, he said.

The particles in the cosmic rays determine how magnetic fields of spatial origin affect their path in space. Understanding their composition is therefore an important part of the difficult task to seek their origins, explains Toshihiro Fujii at Osaka Metropolitan University in Japan.

These unknown origins have created dramatic mysteries such as the cosmic ray of Amaterasu particles. Strangely, it seems to have emerged from a region of space near the Milky Way where there are “no promising astronomical candidates” for its source, he says.

Clark says that it is optimistic about the resolution of many mysteries of this type in a decade, because several new observation instruments, including an Icecube upgrade, will be published online in the near future. “The domain has a really clear vision of the way we arrive at [answering] Some of these questions, ”he says.