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New observations prove that supernova remnants can accelerate protons to energies hundreds of times higher than those of Earth's accelerators.
Abstract
Supernova remnants (SNRs) are considered the primary sources of galactic cosmic rays (CRs), but their ability to accelerate particles up to petaelectronvolt (PeV) energies remains an open question. Here we present high-energy gamma-ray observations of SNR IC 443 with the LHAASO observatory. Morphological analysis reveals a point-like source consistent with a Fermi-LAT compact object showing signs of π0 decay, and an extended source associated with a new Fermi object. The spectrum of the point-like source is described by a power law with an index of ~3.0 and extends beyond 30 TeV with no apparent cutoff. Assuming a hadronic origin, the 95% lower limit on proton energy reaches ~300 TeV. The extended source may be connected to IC 443, SNR G189.6+3.3, or the pulsar wind nebula CXOU J061705.3+222127, and is compatible with both hadronic and leptonic models involving particles of hundreds of TeV. These results provide compelling evidence for efficient acceleration of sub-PeV CRs by SNR shock waves.
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When a massive star explodes, its matter spreads across light-years, forming a supernova remnant — a giant cloud of superheated gas. One such object, IC 443, has long been suspected of churning out particles with colossal energies. But evidence was lacking.
New data from the LHAASO observatory, which captures the most intense cosmic radiation, showed that IC 443 contains a compact source whose radiation reveals the presence of protons with energies hundreds of times greater than those achievable by Earth's accelerators. Nearby, a pulsar may be at work — a super-dense neutron star spinning rapidly and emitting powerful radiation.
The Fermi telescope previously noticed radiation here characteristic of head-on collisions between protons and interstellar gas — a telltale sign of an active particle factory.
This discovery proves: supernova remnants are the main suppliers of cosmic rays, the particles bombarding Earth. The acceleration in IC 443 shows no signs of slowing down, as if the factory has been running non-stop for thousands of years.
🎯 Protons accelerated to such speeds cross our Galaxy in just a few thousand years — instead of the millions it would take an ordinary particle.
