Physicists from the Technical University of Munich (TUM) have discovered evidence of a supernova that exploded near (on a cosmic scale) the Earth around 2.5 million years ago. A supernova happens to stars with a mass of more than ten times that of our sun at the end of their lives. The massive explosion creates heavy elements such as manganese and others.
A research team led by TUM physicists has now confirmed the existence of both iron-60 and manganese-53 in layers of Earth’s manganese crust that are around 2.5 million years old. The researchers say that the increased concentrations of manganese-53 are a “smoking gun,” proving that supernova did occur.
Had a supernova occurred very close to the Earth, it could have inflicted massive damage on the planet and any life on the planet at the time. However, this particular supernova was far enough away that the only side effect was a boost to cosmic rays for several thousand years. Researcher Dr. Thomas Faestermann says that boosting cosmic rays could lead to increased cloud formation and theorizes that there could be a link to the Pleistocene epoch, the period of the ice ages that began 2.6 million years ago.
Typically on Earth, manganese occurs only as manganese-55. Manganese-53 comes from cosmic dust, such as that found in the asteroid belt in our solar system. That dust hits the Earth continuously, but the planet is rarely hit with larger specks of dust. Researchers say that the sediment layers on the seafloor preserve the distribution of elements in the manganese crust and sediment samples.
The team used accelerator mass spectrometry to detect iron-60 and increased levels of manganese-53 in layers deposited about 2.5 million years ago. The researchers note that this is investigative ultra-trace analysis, and they are only talking about a few atoms. However, accelerator mass spectrometry is sensitive enough for scientists to calculate that the mass of the star that exploded had to be around 11 to 25 times the sun’s size.