China's Large High Altitude Air Shower Observatory (LHAASO) has unveiled a detailed high-energy gamma-ray map of the Milky Way, marking a milestone in the search for the origin of cosmic rays. Through its "Mini Survey of the Milky Way," LHAASO offers the most sensitive view yet of the galaxy in teraelectronvolt (TeV) to petaelectronvolt (PeV) gamma rays.
Cosmic rays, high-speed charged par by Riko Seibo
Tokyo, Japan (SPX) Jul 02, 2025
China's Large High Altitude Air Shower Observatory (LHAASO) has unveiled a detailed high-energy gamma-ray map of the Milky Way, marking a milestone in the search for the origin of cosmic rays. Through its "Mini Survey of the Milky Way," LHAASO offers the most sensitive view yet of the galaxy in teraelectronvolt (TeV) to petaelectronvolt (PeV) gamma rays.
Cosmic rays, high-speed charged particles from deep space, carry clues to powerful astrophysical sources like supernova remnants, pulsar wind nebulae, and young star clusters. These particles reach energies billions of times greater than human-made accelerators. However, because magnetic fields bend their paths, detecting associated neutral gamma rays is key to tracing their origins.
LHAASO, designed and built in China, spans a square kilometer with over 6,000 detectors, including KM2A particle sensors, a water Cherenkov array (WCDA), and a wide-field telescope system (WFCTA). It records particle showers triggered by gamma rays hitting Earth's atmosphere, allowing scientists to reconstruct the gamma-ray sky with unparalleled precision.
Its first galactic survey revealed several major findings. In the star-forming region W43-responsible for 10% of the galaxy's star formation-LHAASO detected gamma rays above 100 TeV from a 50-light-year emission zone. The data suggest stellar winds and supernova shocks drive cosmic-ray acceleration there, with the region storing over 2.5+ 10^48 erg of energy, equivalent to 20 million years of solar output.
Another discovery came from CTA-1, a supernova remnant 4,600 light-years away. LHAASO measured 300 TeV gamma rays primarily from its pulsar wind nebula (PWN). Modeling shows electrons are transported by the pulsar wind under weak magnetic confinement (~4.5 microgauss), contradicting traditional expectations.
Near pulsar J0248+6021, researchers identified a diffuse gamma-ray halo extending nearly 50 light-years. The emission may represent the youngest known pulsar halo, offering a rare glimpse into how pulsars evolve and inject energy into the surrounding interstellar medium.
LHAASO also detected an enigmatic source, 1LHAASO J0056+6346u, linked to nearby gas bubbles. Its true nature remains unknown, but may involve hidden pulsar activity or past stellar explosions. Follow-up observations across X-ray and other wavelengths are planned.
"LHAASO is revolutionizing our understanding of the Milky Way and challenging traditional cosmic-ray theories," said Prof. Elena Amato of the Arcetri Astrophysical Observatory. The findings, described by researchers as a "Rosetta Stone" for decoding extreme astrophysics, appear in a special Science China journal collection.
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