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

A 42-light-year X-ray tail links a pulsar to previously 'orphan' gamma rays. The observation was made using the Einstein Probe and LHAASO, two high-energy observatories. The tail extends about 42 light-years and matches the direction of ultrahigh-energy gamma-ray emission detected by LHAASO. This indicates that high-energy particles from the pulsar wind nebula do not immediately diffuse isotropically after leaving their source but instead travel in a preferred direction for tens of light-years. The findings provide new evidence for how high-energy particles escape their acceleration sites and propagate through interstellar space. The tail is the longest of its kind for a pulsar wind nebula and shows that high-energy particles can maintain a clear propagation direction over large distances.

• The tail is 42 light-years long and extends southwest from near the pulsar.
• The tail is observed using the Einstein Probe, which has a wide field of view and low background.
• The tail is detected in both X-rays and ultrahigh-energy gamma rays, suggesting the same population of high-energy particles is responsible.

This discovery offers a new perspective on ultrahigh-energy gamma-ray sources, showing that their locations may not be their birthplaces but rather traces of their long journeys. The study connects observations in two different bands—X-rays and ultrahigh-energy gamma rays—and demonstrates the advantages of coordinated space-borne and ground-based high-energy observatories. It also opens a new window for studying how high-energy particles produced by extreme objects escape their sources and propagate through the Milky Way.

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