LONDON (Reuters) - An international team of astronomers believe they have solved a mystery that has been perplexing scientists for 100 years -- the origin of cosmic rays. Scientists first discovered the energetic particles that bombard the Earth nearly a century ago but where they come from has been one of the big questions in astrophysics. Using an array of four telescopes in Africa, the scientists produced the first image showing that the source of cosmic rays could be the remnant of a supernova, a powerful explosion of a star at the end of its life. "This is the first...