IC 443 is a supernova remnant in Gemini, the expanding wreckage of a massive star that exploded between 3,000 and 30,000 years ago. It lies roughly 5,000 light-years away and its distinctive filamentary structure results from the blast wave colliding with clouds of interstellar gas at very different densities. A neutron star — the crushed stellar core left behind by the explosion — has been identified at its southern edge.