One of the largest known stars in the universe underwent a dramatic transformation in 2014, new research shows, and may be preparing to explode. A study led by Gonzalo Muñoz-Sanchez at the National Observatory of Athens, published in Nature Astronomy today, argues that the enormous star WOH G64 has transitioned from a red supergiant to a rare yellow hypergiant—in what may be evidence of an impending supernova.

The evidence suggests we may be witnessing, in real time, a massive star shedding its outer layers, shrinking as it heats up, and moving closer to the end of its short life.