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Scientists have been left baffled after discovering something vast and radioactive lurking in the depths of the Pacific Ocean. An international team of scientists has found unexpectedly high levels of the rare radioactive isotope beryllium-10 in samples from the Pacific seabed. And they believe it could have been caused by a blast of radiation from space more than 10 million years ago. Beryllium-10 is an isotope - a variant of an element with a different number of neutrons in its atomic nuclei, formed when cosmic rays hit oxygen and nitrogen in the upper atmosphere. After forming, this isotope falls to...

Martin Bizzarro of the University of Copenhagen and his colleagues set out to determine the amount of iron in the early solar system. To do so, they measured nickel-60, a decay product of iron-60, in eight meteorites known to have formed at different times during the first 3 million years of the solar system. The meteorites that formed more than about a million years after the start of the solar system contain significantly more nickel-60 than do those that formed earlier, the team found. In a neighborhood of young stars, only a supernova could have produced iron-60, the parent of...