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 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 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.
The findings have been published in the Proceedings of the National Academy of Sciences.