World First: Scientists Successfully Observe the Interior of an Exploding Star

Supernova, first drew attention thanks to its unusual radiance detected by Zwicky Transient Facility in California. It was not until a few hours later, thanks to a specter obtained at the WM Keck observatory in Hawaii, that the researchers understood that they were faced with an unprecedented phenomenon. The analysis revealed the dominant presence of heavy elements such as silicon, sulfur and argon, signatures rarely observed during a stellar explosion.

Usually, supernovas highlight lighter elements such as helium or oxygen, located in the external layers of the star. Now here, it was the deepest strata that found themselves exposed. This anomaly suggests a loss of massive matter long before the final explosion. Science News reports that the speed of certain atoms reached 3,000 kilometers per second, a sign of a violent ejection preceding the death of the star.

What the internal structure of supernovas reveals

The giant stars live in fusion cycles which transform the light elements into increasingly heavy elements. This evolution shapes a stack of layers similar to an onion, with silicon and sulfur close to the nucleus, then oxygen, carbon and finally hydrogen and helium on the surface. When a star dies, it is generally the external layers that explode and disperse in space. But this time, the 2021YF star had already been stripped up to its internal nucleus, directly revealing the products of its final nuclear merger.

The study published in the journal Nature indicates that the supernova observed comes from a star who has probably lost its hydrogen layer for a long time, but also a large part of its internal envelopes. This allows for the first time to empirically validate the existence and the composition of the deepest layers of the massive stars, whose theories postulate existence without ever having seen them directly. This result confirms that elements such as silicon and sulfur are not only produced but also expelled at the very end of the stellar cycle.

A rare phenomenon to cosmic implications

This extreme stripping of the star raises a major question. How can a star strip at this point before dying? According to the international team led by Steve Schulze at Northwestern University, several scenarios are envisaged. A series of internal eruptions triggered by a phenomenon called “pairs instability” could have projected outwards successive material shells. Some researchers also consider that a companion star has torn off the external layers.

In any case, this event moves away from known patterns. Space.com reports that this discovery encourages to review certain hypotheses on the end of life of very massive stars, which can reach up to a hundred times the mass of the sun. The team at the origin of this discovery admits that their models are not enough to explain entirely what they have observed. This “bare” supernova does not call into question the structure in stars of stars, but suggests that certain evolutionary trajectories are more violent, more complex and more rare than we imagined.

AP News also points out that this explosion could inaugurate a new class of extreme supernovas. It is still too early to say that this case is representative, but it may well be only the first piece of a much larger cosmic puzzle.