Was the Birth of the Sun Natural or Induced?
The Sun was formed about 4.6 billion years ago from a giant molecular cloud. There are a number of ways this might have happened. The cloud first fragments into a ribbon of dense cores. The cores may then condense naturally under their own weight. Or a compression shockwave from a nearby supernova might induce one or more cores to collapse.
A supernova explosion produces a broad range of exotic elements, including many radioactive isotopes such as 26Al, an isotope of aluminium. This decays with a half-life of 720,000 years to produce a stable isotope of magnesium, 26Mg. So, any 26Al produced in a supernova would have long since decayed away.
But if the core that gave birth to the Sun had contained 26Al from a supernova, it would have left a calling-card in the form of an enrichment of 26Mg compared with the most common isotope, 24Mg. Studies of magnesium isotope ratios in the Allende meteorite suggest that this is indeed how it happened. Computer simulations indicate that it would take just 18,000 years to enrich a ten solar mass cloud core with 26Al from a supernova 16 light-years distant. Studies of other isotopes paint a similar picture.
The evidence suggests an induced labour.