Scientists fix astronomical clock to measure cosmic time better

Scientists have settled a long-running debate about one of the tools astronomers use to measure cosmic time.

The new, accurate figure for the iron-60 half-life will bring clarity to many details of how the heavy elements were formed during the evolution of the galaxy.

These scientists said that they now have a better figure for the time it takes this isotope to decay by half. They found that the half-life of iron-60 was 2.6 million years, resolving the large discrepancy between two previous measurements that found values of 1.5 million years and 2.62 million years respectively.

Dr. Anton Wallner, from the Australian National University Research School of Physics and Engineering, said that the iron-60 half-life was integral to theories about supernovae and the early solar system, because iron-60 was formed predominantly in supernovae its presence on Earth was thought to indicate that there were nearby supernovae in the last 10 million years.

These might have had an effect on Earth's climate or even triggered the birth of the solar system more than 4 billion years ago, he further added.

Most iron-60 was formed in massive stars, which explode at the end of their lives in a supernova event, spreading the radioactive element through space.

Today iron-60 can be observed directly in our Milky Way through characteristic radiation emitted during its radioactive decay, indicating where recent supernovae have created new elements.

The slow decay of iron-60 makes it difficult to measure the decay time precisely. The team used a unique mass spectrometer system at the Heavy Ion Accelerator Facility at ANU, which was more sensitive than previous experiments.