The vast solar system that contains Earth is not older than scientists had thought, but it apparently developed faster than they surmised, according to an international team of researchers from the Hebrew University of Jerusalem and universities and laboratories in the US and Japan.The astronomical team, who published their findings in a recent issue of the prestigious journal Science, said that the solar system indeed came into being some 4.5 billion years after the Big Bang, but its formation took a shorter time than researchers had thought.Establishing chronologies of past events or determining ages of objects need clocks that tick at different paces, according to how far back one looks. Nuclear clocks, which are used for such dating, are based on the rate of decay of an atomic nucleus expressed by a half-life – the time it takes for half of a number of nuclei to decay. Each nuclear species has its own half-life.Radiocarbon dating, which was invented in Chicago more than six decades ago and has been refined ever since, can determine when artifacts even from prehistoric times originated because the half-life of radiocarbon (carbon-14) is a few thousand years. The evaluation of ages of the history of earth or of the solar system requires extremely “slow-paced” chronometers consisting of nuclear clocks with much longer half-lives.HU nuclear physicist Prof. Michael Paul, as well as researchers from the University of Notre Dame and the Argonne National Laboratory in the US and two Japanese universities, conducted the research.The main tool for establishing the time evolution of the solar system over its first few hundred million years is called 146Sm, which belongs to a family of nuclear species that were “alive” in our sun and its solar system when they were “born.”Events that occurred later, within a few hundred million years, are dated by the amount of 146Sm that was left in various mineral archives until its eventual “extinction.”This by itself is due to a delicate geochemical property of samarium, a rare element in nature. It is a sensitive probe for the separation, or differentiation, of the silicate portion of Earth and of other planetary bodies.The main result of the team’s work is a new determination of the half-life of 146Sm, which was previously recognized as 103 million years, to a much shorter value of 68 million years.The shorter half-life value, like a clock ticking faster, has the effect of shrinking the assessed chronology of events in the early solar system and in planetary differentiation into a shorter time span.The new time scale is now consistent with recent and precise dating made on a lunar rock and is in better agreement with the dating obtained with other chronometers. The measurement of the tool’s half-life, performed over several years by the collaborators, involved the use of the ATLAS particle accelerator at the Argonne National Laboratory in Illinois.