We thought we knew how powerful supernova explosions could be. We also thought that supernovae and γ -ray bursts were unrelated. One extraordinary supernova is making us re-examine these Ideas. Supernovae are the explosive death throes of massive stars, and they produce the elements that the Earth and you and I are made of. In a 'core-collapse' supernova — one of two main types — the star's core becomes so large that it collapses. The mass of electrons and nuclei becomes compressed into a neutron star, a tiny ball of neutrons about ten kilometres across; that releases a vast amount of gravitational energy into the surrounding material, blowing it outwards. For a few weeks a single star becomes as bright as a galaxy of 100 billion ordinary stars. Supernovae release their energy in many forms: neutrinos, the kinetic energy of the debris, optical light and radio waves.
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