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Academic Minute

Dr. Michael Paul, Hebrew University of Jerusalem – Dating the Solar System

In today’s Academic Minute, Dr. Michael Paul of the Hebrew University of Jerusalem explains how a recently refined measurement has provided a better picture of the early solar system.

Michael Paul is the Kalman and Malke Cooper Professor of Nuclear Physics at the Hebrew University of Jerusalem and a research associate and visiting scientist at the Argonne National Laboratory. His current research is focused on measuring long-lived radionuclides in nature and in the environment by accelerator mass spectrometry (AMS), as well as the application of AMS to nuclear and atomic physics, geophysics, biomedicine and environmental sciences. He holds a Ph.D. from Hebrew University.

About Dr. Paul

Dr. Michael Paul, Hebrew University of Jerusalem – Dating the Solar System

Establishing chronologies of past events or determining ages of objects, requires having clocks that tick at different paces, according to how farback one looks. Nuclear clocks used for dating - are based on the rate of decay of an atomic nucleus expressed by a half-life, the time it takes for half of the nuclei to decay. Radiocarbon dating for example, invented in Chicago in the late 40s, can date archaeological artifacts because the half-life of radiocarbon or carbon-14 is of a few thousand years. Our Solar System is four and a half - billion years old and the evaluation of ages over the history of Earth - or the Solar System - requires extremely “slow-paced” clocks.

We determined the pace, or the half-life of one these clocks, the nucleus Sm-146, which belongs to a group of nuclei which were live in  the Early Solar system - but have since totally decayed. Sm-146 has become the main tool for establishing the time evolution of the Solar System over its first few Hundred million years.

Our result shows that the half-life of Sm-146 is shorter by a third than What Was adopted before, 68 million instead of 103 million years. This clock, with a faster tick, shrinks therefore our chronology of the Early Solar System to a shorter time span. The differentiation of planets like our Earth and formation of rocks on Earth, but also on the Moon and on Mars, are now estimated to have occurred at earlier times after formation of the Solar System, not more than 200 million years.

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