When a star dies, there is a massive explosion that shoots star particles into space, known as a supernova. Upon each explosion, new chemical elements are created by the explosion itself. At least one such occurrence has taken place near our solar system about two million years ago.
Recent evidence found on Earth allowed scientists to confidently say such an event took place. Within the Pacific Ocean deep-sea crusts and in the ocean floor, samples show increased concentration of the iron isotope known as 60Fe.
60Fe is a radioactive isotope and is created mainly through supernova explosions. Since the half life of this isotope is 2.62 million years, any radioactive 60Fe currently on the planet did not come from the birth of the solar system. Such samples would have long ago decayed, turning into stable elements, leaving behind no sign of their existence on Earth.
The famous supernova hypothesis was first put into play in 1999 by Technical University of Munich (TUM) researchers who had discovered evidence within deep-sea crusts. Thanks to new findings, physicians at the Technical University of Munich and USA colleagues have located a very large concentration of 60Fe in lunar ground samples. These samples were gathered between the years 1969 and 1972 during the Apollo lunar missions 12, 15 and 16. At this time, the lunar material was transported back to Earth.
Researchers say it is completely possible that 60Fe can be present on the moon due to massive amounts of cosmic particles. Such particles do not break up when colliding with air molecules on the moon as they would in the presents of Earth’s atmosphere. Unlike on the Earth, these tiny particles directly impact the surface of the moon and cause transmutation. Dr. Gunther Korschinek, physicist at TUM and scientist of the Cluster of Excellence Structure and Origin of the Universe wants to be clear that this can only account for a very small amount of the 60Fe that has been found. He says it is his belief that the 60Fe that has been found in both terrestrial and lunar samples is coming from the same source. Since the deposits have been created more recently, it can be assumed they were created by supernovae, whether one or more is uncertain at this time.
The Moon is a much easier place to determine cosmic records when compared to Earth, giving scientists the ability to distinguish both upper and lower limits for the flow of 60Fe that made its way to the Moon. These findings make it possible for researchers to accurately calculate the distance to the supernova. Korschinek says the measured 60Fe flow directly corresponds with a supernova at about 300 light years from the target. This number coincides with a theoretical estimation that was recently published in Nature.
All lunar sample studies investigated all samples using high-sensitivity accelerator mass spectrometer currently housed at the Maier-Leibnitz Laboratory near Munich. The research was funded by the German Research Foundation.