Ancient star explosions revealed in the deep sea

A mystery surrounding the space around our solar system is unfolding thanks to evidence of supernovae found in deep-sea sediments. Professor Anton Wallner, a nuclear physicist at ANU, led the study which shows the Earth has been travelling for the last 33,000 years through a cloud of faintly radioactive dust.   "These clouds could be remnants of previous supernova explosions, a powerful and super bright explosion of a star," Professor Wallner said. Professor Wallner conducted the research at the ANU Heavy Ion Accelerator Facility (HIAF). He also holds joint positions at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Technical University Dresden (TUD) in Germany. The researchers searched through several deep-sea sediments from two different locations that date back 33,000 years using the extreme sensitivity of HIAF's mass spectrometer. They found clear traces of the isotope iron-60, which is formed when stars die in supernova explosions. Iron-60 is radioactive and completely decays away within 15 million years, which means any iron-60 found on the earth must have been formed much later than the rest of the 4.6-billion-year old earth and arrived here from nearby supernovae before settling on the ocean floor. Professor Wallner  previously found  traces of iron-60 at about 2.6 million years ago, and possibly another at around 6 million years ago, suggesting earth had travelled through fallout clouds from nearby supernovae.