The recent discovery of plutonium-244 in the deep sea has sparked a new mystery in the field of astronomy. This rare element, produced by violent cosmic explosions, has led scientists to question the nature of the event that created it. The findings, published in Nature, suggest that the explosion was more powerful than a standard supernova, as evidenced by the presence of plutonium-244. However, the absence of curium-247, another radioactive element created in giant explosions, has led to a deeper investigation into the nature of the event.
Dr. Dominik Koll, a researcher at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany, led the study. He explains that the explosion was at least 100 million years ago and produced some of the rarest elements in the universe, which eventually reached Earth and settled at the bottom of the ocean. The team's findings are significant because they challenge existing models of cosmic events and raise new questions about the nature of supernovae and neutron star collisions.
One of the most intriguing aspects of the study is the use of dating techniques similar to carbon dating, but using other radioactive elements. The team isolated iron-60, a tracer of supernovae, from a sample of ferromanganese crust extracted from the Pacific Ocean floor. By combining this data with detailed modeling of the age of the sample layers, they found peaks of iron-60 at two specific depths in the crust, pointing to two nearby supernovae in the last ten million years.
However, the data did not match the initial hypothesis that the plutonium-244 had been created in the same explosions. Instead, the plutonium-244 was evenly spread throughout the sample, suggesting an older event that had spread its debris more evenly across the space around Earth (the interstellar medium). This led the team to look for curium-247, which is also radioactive and created only in giant explosions. The absence of curium-247, with its shorter half-life, suggests that the event happened long enough ago for it all to decay, pushing back the date of the event to 100 million years ago, or more.
Dr. Koll's findings have sent theorists back to the drawing board, as they have ruled out four models, including a recently proposed collision of the Solar System with a dense interstellar cloud. He emphasizes the need for more models and experiments to get to the truth, as the interstellar medium is more complicated than previously thought. The study highlights the importance of careful detective work and the use of dating techniques to unravel the mysteries of the cosmos.
