A star exploded – and for the first time, we got a good look inside. When a massive star 2.2 billion light-years away reached the end of its life and exploded in a brilliant burst of light, astronomers analyzing the debris didn’t see the usual outer layers of hydrogen, helium, or oxygen. They saw silicon. Sulfur. Argon. Elements that normally lie buried deep inside a star’s core. This wasn’t supposed to be possible. According to stellar models, massive stars are built like onions. Hydrogen and h