Nuclear Physicist Gunther Korschinek and his team of researchers from Technical University of Munich sifted through half-a-ton of snow from Antarctica to find 10 atoms(!) of Iron-60 an isotope (radioactive 60 protons, 60 neutrons in the nucleus) only produced in supernova explosions.
Their study of the deposit indicates the 60Fe only recently arrived (likely in the past few decades).
60Fe has been detected before in ocean sediments, on the moon and in meteorites but those deposits are a few millions years old.
Shock waves from stellar explosions must carry the 60Fe through space and we happened to be in the path of the traveling shock waves.
A diminishing amount of sunlight by mid-August triggers trees to start closing down – triggering a hormone that releases a chemical message to each leaf that it is time to prepare for winter. Over the next few weeks, abscission cells form a bumpy line at the place where the leaf stem meets the branch. And slowly, but surely, the leaf is “pushed” from the tree branch. This winterization process ensures trees’ survival. In spring and summer, leaves convert sunlight into energy through photosynthesis.
During that process, the trees lose so much water that when winter arrives, the trees are no longer able to get enough water to replace it.