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Inside IC 443, 5,000 light-years from Earth, two patches of high-energy light mark where the remnant still acts on nearby gas.<\/p>\n
By tracing those gamma rays, the LHAASO<\/a> Collaboration tied the compact patch to fast protons striking surrounding material.<\/p>\n That signal extends beyond 30 trillion electron volts without a clear cutoff. This shows that the accelerator has not yet run out of power.<\/p>\n The discovery strengthens IC 443 as a cosmic-ray source, but the second glow still needs a wider explanation.<\/p>\n Tracing cosmic signals<\/p>\n Cosmic rays, fast charged particles from space, cannot point back to their birthplace because magnetic fields bend their paths.<\/p>\n When protons crash into gas, they create unstable particles that break into gamma rays<\/a>. These rays travel more directly through space.<\/p>\n Such light gave the team a cleaner signal than the protons themselves, even though the signal still needed careful sorting.<\/p>\n That sorting mattered because the remnant sits near other energetic objects, and overlapping signals can make one source look like two.<\/p>\n Clues from collisions<\/p>\n A supernova remnant, the expanding debris of an exploded star, can keep driving shock waves through nearby gas for thousands of years.<\/p>\n Those shocks squeeze magnetic fields and scatter particles back and forth, so protons gain energy in repeated passes.<\/p>\n IC 443 is especially useful because molecular clouds, cold gas clouds where stars can form, still crowd its edges and give accelerated protons something to hit.<\/p>\n Crowded gas boosts the gamma-ray output, but it also makes the region harder to interpret clearly.<\/p>\n LHAASO isolates sources<\/p>\n High on Haizi Mountain, in Sichuan Province, China, LHAASO watches particle showers created when gamma rays strike the atmosphere.<\/p>\n Its detectors cover a wide sky view and separate incoming light by energy, direction, and shower shape.<\/p>\n For IC 443, the team used years of data and separated a compact, point-like source from a broader region of high-energy emission.<\/p>\n That split kept the strongest proton claim tied to the compact source rather than the whole glowing region.<\/p>\n Old clue revisited<\/p>\n In 2013, a Fermi Large Area Telescope result<\/a>, from NASA\u2019s gamma-ray space instrument, caught the pion signature in IC 443.<\/p>\n That earlier signal proved protons were colliding with gas, but it did not show the highest energy they could reach.<\/p>\n \u201cThe direct detection of pion-decay signatures in supernova remnants closes the loop and provides dramatic observational evidence for a significant component of cosmic rays,\u201d said Jerry Ostriker, an astrophysicist at Columbia University<\/a>.<\/p>\n LHAASO now extends that evidence upward, from lower-energy clues to photons tens of trillions of electron volts strong.<\/p>\n Why 300 TeV matters<\/p>\n One teraelectronvolt (TeV) equals one trillion electron volts, so 300 TeV marks a far higher proton scale.<\/p>\n Because gamma rays carry only part of a proton collision\u2019s energy, the parent protons must be far stronger.<\/p>\n The 95% lower limit reaches about 300 TeV, meaning the best fit could go higher without breaking the data.<\/p>\n That level remains below the cosmic-ray knee<\/a> where the particle count steepens near 3.67 quadrillion electron volts, yet it narrows the gap.<\/p>\n Mystery of second glow<\/p>\n A wider glow of high-energy light overlaps another possible remnant and a compact X-ray object in the same region.<\/p>\n Its spectrum reaches similar energies, but the pattern does not point to a single clear origin.<\/p>\n Protons escaping through nearby gas could produce it, while energetic electrons could also boost background light into gamma rays.<\/p>\n That uncertainty keeps the strongest claim tied to the compact source, where the proton-collision evidence is most direct.<\/p>\n Evidence has limits<\/p>\n Strong evidence does not make the compact source<\/a> a finished case, because a hadronic origin, gamma rays made by proton collisions, remains an assumption.<\/p>\n They checked whether the signal still appeared after accounting for background light from the Galaxy and nearby sources.<\/p>\n Those checks shifted some details but left the compact source consistent within the main reported statistical errors.<\/p>\n The remaining caution centers on the wider glow, where several physical explanations still fit the same data.<\/p>\n Testing the signals<\/p>\n Sharper maps can test whether the wider emission follows dense gas, an older remnant, or a neutron star, a dense collapsed stellar core.<\/p>\n Radio, X-ray, and gamma-ray observations can compare shapes, because different particles light up different materials and energies.<\/p>\n A tighter match with gas would strengthen the proton<\/a> case, while a broader, smoother glow would favor energetic electrons.<\/p>\n Either outcome would make IC 443 a cleaner guide to how stellar explosions feed the Galaxy\u2019s particle population.<\/p>\n A sharper cosmic map<\/p>\n IC 443 now links an old explosion, dense gas, and gamma rays into a sharper test of cosmic-ray acceleration.<\/p>\n The compact source points to protons reaching at least 300 TeV, while the wider glow preserves the main limit.<\/p>\n The study is published in Physical Review Letters<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read?\u00a0Subscribe to our newsletter<\/a>\u00a0for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on\u00a0EarthSnap<\/a>, a free app brought to you by\u00a0Eric Ralls<\/a>\u00a0and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"A new study has found that IC 443, the expanding debris of an exploded star, is accelerating 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