more than 100 trillion electron volts

from: The highest-energy photons ever seen hail from the Crab Nebula
Some of the supernova remnant’s gamma rays have more than 100 trillion electron volts of energy

https://www.sciencenews.org/article/highest-energy-photons-ever-seen-hail-crab-nebula

Physicists have spotted the highest-energy light ever seen. It emanated from the roiling remains left behind when a star exploded.

This light made its way to Earth from the Crab Nebula, a remnant of a stellar explosion, or supernova, about 6,500 light-years away in the Milky Way. The Tibet AS-gamma experiment caught multiple particles of light — or photons — from the nebula with energies higher than 100 trillion electron volts, researchers report in a study accepted in Physical Review Letters. Visible light, for comparison, has just a few electron volts of energy.

Although scientists have searched for photons at these energies before, they haven’t succeeded in detecting such energetic photons until now, says astrophysicist Petra Huentemeyer of Michigan Technological University in Houghton, who was not involved with the research. For physicists who study this high-energy light, known as gamma rays, “it’s an exciting time,” she says.

In space, supernova remnants and other cosmic accelerators can boost subatomic particles such as electrons, photons and protons to extreme energies… “The question is: How does nature do it?” says physicist David Hanna of McGill University in Montreal.

In the Crab Nebula, the initial explosion set up the conditions for acceleration, with magnetic fields and shock waves plowing through space, giving an energy boost to charged particles such as electrons. Low-energy photons in the vicinity get kicked to high energies when they collide with the speedy electrons, and ultimately, some of those photons make their way to Earth.

…

Previous experiments have glimpsed photons with nearly a trillion electron volts. Now, after about three years of gathering data, the researchers found 24 seemingly photon-initiated showers above 100 trillion electron volts, and some with energies as high as 450 TeV.

Looking for photons of ever higher energies could help scientists nail down the details of how the particles are accelerated. “There has to be a limit to how high the energy of the photons can go,” Hanna says. If scientists can pinpoint that maximum energy, that could help distinguish between various theoretical tweaks to how the particles get their oomph.