Science Speaker Series - Featuring Dr. Brian Fields, Prof. of Astronomy at University of Illinois

"When Stars Attack! Near-Earth Supernova Explosions and Their Radioactive Fingerprints"
The most massive stars are the celebrities of the cosmos: they represent a small fraction of all stars, but live extravagant lives and die in spectacular and violent supernova explosions. While these events are awesome to observe, they can take a sinister shade when they occur closer to home, because an explosion within a certain "minimum safe distance" would pose a grave threat to Earthlings. We will discuss these cosmic threats to life and show compelling evidence of “near miss” supernova explosions from three and seven million years ago that both rained their debris upon the Earth. This discovery allows us to study supernova ashes in the laboratory and confirms that nearby explosions are a fact of life in our Galaxy. We then press further, presenting recent evidence that supernova explosions could have caused biological extinctions on Earth around 360 million years ago. We conclude with tests of this hypothesis, including the search for trace amounts of radioactive supernova by-products in fossils that witnessed the end of the Devonian period.
Brian Fields is a professor of Astronomy at the University of Illinois, where he also is an affiliate Professor of Physics. He studies the "inner space/outer space" connections that link the science at the smallest and largest scales. He is particularly interested in the highest-energy sites in nature ̶ the big bang, exploding stars (supernovae), and high-energy particles in space (cosmic rays) ̶ where all fundamental forces play essential roles. He is fascinated by the way that the human narrative is ultimately linked to that of cosmic events that largely pass unremarked but ultimately shape our lives.