Scientists have, for the first time, observed the inside of a dying star as it exploded, providing a rare glimpse into stellar evolution. Stars can live for millions to trillions of years until they run out of fuel. 

The most massive ones end their lives with a bang in an explosion called a supernova. Using telescopes that look deep into space, researchers have seen many such explosions. These cosmic outbursts often mix up a dying star's layers, making it difficult for scientists to see the inner structure. But this was not the case for a new discovery: a supernova named 2021yfj, located in our Milky Way galaxy. 

The outer layers of hydrogen and helium had long since peeled away from the collapsing star, which wasn't surprising. However, the star's dense, innermost layers of silicon and sulfur also shed during the explosion.

 "We have never observed a star that was stripped to this amount," said Northwestern University's Steve Schulze, who was part of the team that discovered this and published their findings on Wednesday in the journal Nature. 

This discovery supports ideas scientists have about what large stars look like near the end of their lives, organized into layers of lighter elements on the outside and heavier ones near the core. "Because so many of the layers had been stripped off this star, this basically confirmed what those layers were," said Anya Nugent, a supernova researcher at the Harvard-Smithsonian Center for Astrophysics, who was not involved with the new research.

 It is still unclear how this star lost so much material – whether its layers were violently flung off in its final stages or pulled away by a companion star. Future studies may offer answers, though scientists acknowledge that such an event might be difficult to observe again.