Predicting the death of a star is easy.  If we know how massive it is, and what stage of life it’s in, we know that it should explode eventually, within a set timeframe of many hundreds of thousands, or even millions of years.  But on human timescales, that is just not good enough.  What if we could predict a supernova explosion within a few months? For something that lives for so long, this would be a triumph in our understanding of the universe.  Over the past couple of years, this is exactly what happened.  Here’s how. A supernova is one of the most...