Wind and turbulent fossils surrounding newly formed stars likely emit the fastest particles.
Neutron-gravitational stars known as pulsars blow fast and robust magnetic fields. When charged particles, mainly electrons, are trapped in such turbulent conditions, they can be developed into more powerful ones, reported astronomers on April 28 in The Astrophysical Journal Letters. In addition, those electron electrons can further magnify the surrounding light into equally powerful energy, possibly producing high-energy gamma-ray photons that have led astronomers to discover these molecular launchers in the first place.
“This is the first step in exploring the link between pulsars and ultrahigh-energy emissions,” said astronomer Ke Fang of the University of Wisconsin, Madison, who was not involved in the new project.
Last year, researchers at the Large High Altitude Air Shower Observatory, or LHAASO, in China announced the discovery of the strongest gamma rays ever detected, reaching 1.4 quadrillion electron volts (SN: 2/2/21). That is almost 100 times stronger than the most oversized particle fastener, the Large Hadron Collider near Geneva. Identifying the cause of this and other intense gamma rays can signal cosmic radiation – energetic protons, heavy atoms, and electrons exploding from Earth from space beyond our solar system.
Some gamma rays are thought to come from the same source as cosmic rays. One production method is that soon after launch, cosmic rays can strike local photons with less energy, amplifying them into more powerful gamma rays. But electrically charged cosmic rays are struck by galactic magnetic fields, which means they do not move in a straight line, thus making it difficult for attempts to trace the tiny particles back to their source. Gamma rays, however, are less resistant to magnets, so astronomers can trace their perilous paths back to their origin – and discover where cosmic rays are formed.
To that end, the LHAASO team tracked hundreds of gamma-ray photons found in 12 spacecraft. While the team identified a single location, such as the Crab Nebula, a supernova fossil of approximately 6,500 light-years from Earth, researchers suggested that some might be associated with other astronomical sites or constellations (SN: 6 / 24/19).
In a new study, astronomer Emma de Oña Wilhelmi and colleagues came up with one of those possible sources: pulsar wind nebulas, turbulent clouds, and charged particles around the pulsar. Researchers were not sure that such structures could produce high-energy particles and light, so they determined to show mathematically that pulsar wind and nebulae were not sources of excessive gamma rays. “But to our surprise, we saw in the worst-case scenario, you can explain all the sources [LHAASO observed],” said de Oña Wilhelmi of the German Electron Synchrotron in Hamburg.
The tiny pulsars in the heart of these nebulae – no more than 200,000 years old – can provide all of that because of their strong magnetic field, which creates a vibrating magnetic field called the magnetosphere.
Any charged particles moving through a magnetic field are fast, says de Oña Wilhelmi. This is how the Large Hadron Collider expands the particles into larger forces (SN: 4/22/22). However, the team calculates a powerful pulsar accelerator can raise particles to an even higher power. This is because electrons escape the pulsar magnetic field and combine with a star-studded explosion’s material and magnetic fields. These magnetic fields can accelerate electrons at even higher speeds, the group receiving them. When those electrons jump into the surrounding photons, they can elevate those light particles into higher energy, producing gamma rays.