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discovered_02_2015 - Portrait: Astronomy under the sea

WWW.HZDR.DE discovered 02.15 PORTRAIT // HZDR visiting scholar Jenny Feige has succeeded in using deep sea sediments to detect ancient star explosions. With her popular science article "Astronomie unter dem Meer" (Astronomy Under the Sea), she won the Klaus Tschira Award for Achievements in Public Understanding of Science in Physics 2015 and 5,000 euros. Text . Tina Schulz ASTRONOMY UNDER THE SEA In her doctoral thesis at the University of Vienna, Jenny Feige proved that when it comes to astronomy it is important to not only observe the sky, but to also look beneath the sea. There, the 34-year-old Brandenburg native studied special, long- lived radionuclides in two to three million year old sediment layers from the Indian Ocean. The radionuclides are a result of nuclear reactions that take place during supernova explosions in space. If such a cosmic explosion were to occur near our solar system, then the radionuclides would reach the Earth as stardust and accumulate in the sediments. "The deep sea archives have a kind of geological long-term memory that stores traces of star explosions that happened a long time ago," the astrophysicist explains. Jenny Feige analyzed her samples using accelerator mass spectrometry - a method that detects individual atoms - in Vienna, at the Australian National University in Canberra, and at HZDR. In certain parts of the sediment cores, her analyses verified the existence of 60 Fe – an iron isotope that does not occur naturally on Earth. In massive stars, it is produced only shortly before and during a supernova. Jenny Feige spent a total of six months in Dresden under the supervision of nuclear chemist Silke Merchel. Here, she mainly made use of the chemical labs to prepare her samples and the accelerator facility DREAMS (DREsden Accelerator Mass Spectrometry). "The detection of 60 Fe alone is not sufficient. We also need to know the exact age. This is why Jenny Feige measured the beryllium isotope 10 Be here as well," Merchel explains. This isotope is produced in the Earth's atmosphere and gradually makes its way down to Earth, where it then decays. "Every sediment layer has more 10 Be atoms than the one below it, in which the decay of the isotope is already more advanced. This can be used to determine the age of the sediments." And Jenny Feige was indeed able to conclusively prove that the 60 Fe had been found only in those sediment layers that are 1.7 to 3.2 million years old. Thus, she also disproved the assumption that only one supernova has occurred near our solar system. "In fact, the signal results from an overlap of multiple supernova remnants," according to Feige. For her doctoral thesis she received the Doctoral Thesis Award of the Nuclear Chemistry Section of the German Chemical Society (GDCh) last year. In her article "Astronomie unter dem Meer", Feige fascinatingly explained an area of research that until now has been widely unknown to the public: deep-sea astronomy. On October 8, 2015 she received the Klaus Tschira Award for Achievements in Public Understanding of Science in Physics for her publication. The Klaus Tschira Foundation has been awarding the prize since 1997 to young scientists who present their results in an especially well-written and generally understandable article. PUBLICATION: J. Feige et al.: "AMS measurements of cosmogenic and supernova-ejected radionuclides in deep-sea sediment cores", in European Physical Journal Web of Conferences 63, 2013 (DOI: 0.1051/epjconf/20136303003) _Helmholtz Institute Freiberg for Resource Technology at HZDR Dr. Silke Merchel _Department of Astronomy and Astrophysics at the TU Berlin (Berlin Institute of Technology) Dr. Jenny Feige CONTACT "The iron isotope 60 Fe is produced at temperatures ranging from 500 million to 2 billion degrees Celsius - conditions that aren't even present at the core of our sun."