The international group of scientists has found heavy radioactive isotopes in the deep-sea korea of the Pacific, confirming that supernovae broke out near the ground. On the tracks of an ancient catastrophe found at a depth of 1500 meters, it is reported in an article published in the SCIENCE journal.
Heavy isotopes occur as a result of the R-process or the rapid process of capturing neutrons, which occur during outbreaks of certain types of supernova or as a result of the merge of neutron stars. To determine which of the two options is the most likely, scientists analyzed the isotopic composition of samples of deep-water rocks to find iron-60 (half-life is 2.6 million years old) and plutonium-224 (half-life is 80.6 million years old). The first isotope is formed in massive stars and is thrown into the interstellar medium with supernoval flashes. Plutonium-224 is made exclusively at R-process.
Scientists have found that in the last 10 million years there are two large infiltration of iron-60, each of which was accompanied by a flow of a smaller amount of Plutonium-224, but in the same ratio. Nevertheless, the revealed amount of plutonium is lower than one could expect if supernovae were, first of all, are responsible for its education, and this indicates the possible contribution of other R processes. For example, this isotope could arise as a result of a more ancient catastrophic event, for example, an explosion on a neutron star. It was kept in the interstellar medium until the shock wave from supernova emissions did not drop him towards the Earth.
Iron-60 peaks in the oceanic cortex correspond to 2-4 supernova flashes, which occurred at a distance of 160-330 light years from the ground.