Artist's impression of Rho Cassiopeiae (Pic: Instituto de Astrofisica de Canarias) A massive and very unstable star in our galaxy is likely to explode any day, ejecting mass equal to 10,000 Earths, astronomers have predicted. The giant star, known as Rho Cassiopeiae, was first observed shedding an equivalent mass of material three years ago by the Isaac Newton Group of Telescopes - more than astronomers have ever witnessed in a single stellar eruption. Recently, they have noted the star exhibiting some of the same behaviour that lead to that explosion. A study of the build-up is published in...