A 42-light-year X-ray tail links a pulsar to previously 'orphan' gamma rays

Scientists have discovered a 42-light-year X-ray tail connected to a pulsar, providing insights into the origin and behavior of high-energy cosmic rays. This finding, published in Science China: Physics, Mechanics & Astronomy, was made possible through joint observations from China's Einstein Probe satellite and the Large High Altitude Air Shower Observatory (LHAASO).

High-energy particles, such as cosmic rays, can be accelerated to near the speed of light near extreme objects like supernova remnants, pulsars, and black holes. These particles then travel through interstellar space, often exhibiting peculiar behavior that is difficult to explain. The Einstein Probe detected a previously unseen X-ray tail extending about 42 light-years from a pulsar called PSR J1740+1000, which is located about 4,600 light-years away from Earth.

Remarkably, this X-ray tail aligns with ultrahigh-energy gamma-ray emissions detected by LHAASO. The particles responsible for these gamma rays are believed to originate in the pulsar wind nebula and gain extremely high energies as they propagate along the tail. As these high-energy electrons move through magnetic fields, they emit synchrotron radiation, which is detected as X-rays by the Einstein Probe.

Simultaneously, the high-energy electrons interact with low-energy photons in space, boosting them to even higher energies and producing the ultrahigh-energy gamma rays observed by LHAASO.

This discovery suggests that the high-energy particles maintain a clear propagation direction over a considerable distance, spanning tens of light-years. Researchers propose two possible explanations for this phenomenon: a highly ordered interstellar magnetic field that allows particles to travel along the field direction, or a fast, collimated outflow ejecting particles in a specific direction, similar to water from a fire hose. Further investigation is needed to determine which mechanism is responsible.

This finding offers new insights into the behavior of high-energy cosmic rays and the propagation of particles in interstellar space. It also provides a potential explanation for ultrahigh-energy gamma-ray sources that lack clear astronomical counterparts. Understanding these processes is crucial for comprehending the origin and acceleration of cosmic rays, as well as their interactions with interstellar matter.