An artists impression of the star WOH G64ESO/L. CaladaOne of the largest stars in the known universe is undergoing a strangely rapid transformation and may soon explode as a supernova.First catalogued in 1981, WOH G64 sits some 160,000 light years from Earth in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way. It is one of the biggest red supergiants, the largest stars we know of. These are massive, cool stars that have run out of hydrogen fuel in their core and instead burn an envelope of hydrogen gas that surrounds them.