A window on nucleosynthesis through detection of short-lived radionuclides

The detection of cosmic γ radioactivity of live nuclides from supernovae remnants during the last decade has had an immense impact on our understanding of stellar nucleosynthesis. It is expected that, similarly, nuclides such as ¹⁴⁶Sm, ²⁴⁴Pu, ¹⁸²Hf, ²⁴⁷Cm with halflives of the order of a few l0⁷ years be present in the Interstellar Medium (ISM) as freshly synthesized matter; they are however not detectable by γ-ray astronomy because of their lower activity. Depending on their steady-state abundance and the ISM influx rate in the solar system, deposition on Earth of these nuclides through cosmic dust and their detection may provide a complementary approach. A search for ²⁴⁴Pu in a deep-sea sediment sample, acting here as repository archive for cosmic dust, was performed by accelerator mass spectrometry (AMS) and an upper limit for deposition of interstellar ²⁴⁴Pu of 0.2 atoms/cm²/yr obtained. Derived constraints on ²⁴⁴Pu abundance in the ISM are discussed. Further development of detection techniques for ²⁴⁴Pu and other nuclides is under way.