By ANDREW RUANO
Staff Writer
Star explosions may have played a greater role in Earth’s climate history than scientists thought. Nearby SuperNovas have left a series of possible fingerprints in the tree-ring record here on Earth over the past 40,000 years, potentially disrupting our planet’s climate multiple times over this span, a new study reports. “These are extreme events, and their potential effects seem to match tree-ring records,” study author Robert Brakenridge, a senior research associate at the Institute of Arctic and Alpine Research at the University of Colorado Boulder, said in a statement. Brakenridge compiled a list of 18 supernovas violent explosions that mark the deaths of certain kinds of stars that occurred within about 4,900 light-years of Earth. He then compared the estimated timing of these cosmic events with spikes in carbon-14, as observed in the tree-ring record. Carbon-14 is a radioactive isotope of carbon that contains eight neutrons in its atomic nucleus instead of the usual six. Carbon-14 is rare on Earth, and it doesn’t occur here naturally without some outside influence namely, high energy radiation streaming in from deep space, which can convert some of the “normal” carbon in our atmosphere to carbon-14. The results are not conclusive, given the various uncertainties involved. For example, it’s difficult to date supernovas precisely; the inferred timing of the Vela explosion may be off by as much as 1,500 years, Brakenridge said. But he thinks that the new results, which were published online last week in the International Journal of Astrobiology, show that more research into a supernova-radiocarbon link is warranted.