by Mary Caperton Morton Monday, August 15, 2016
At the end of a star’s lifecycle it collapses and explodes into a supernova, spewing rare elements and isotopes outward into space. In the last 1,000 years, three supernova events have been observed in the Milky Way Galaxy. Now scientists have detected a rare iron isotope, iron-60, in our solar system that hints that a supernova may have exploded nearby within the last few million years.
Iron-60 was detected by the Cosmic Ray Isotope Spectrometer aboard NASA’s Advanced Composition Explorer, currently orbiting between Earth and the sun. Over the past 17 years of data collection, only 15 of these rare nuclei, thought to only be produced by supernova explosions, have been detected.
Iron-60 is radioactive, with a half-life of 2.6 million years, so the nuclei must have formed in a supernova within the last few million years. The most likely candidate, as reported by astronomer Robert Binns of Washington University in St. Louis and colleagues in Science, is the death of a massive star in the nearby Scorpius-Centaurus Association, about 400 light-years from the sun.
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