A Star Exploded as a Supernova and Then Collapsed Into a Neutron Star. But Only a Fraction of its Matter was Released

"We saw this massive star's core collapse, but we saw remarkably little mass ejected. We call this an ultra-stripped envelope supernova and it has long been predicted that they exist. This is the first time we have convincingly seen core collapse of a massive star that is so devoid of matter."

"You need fast transient surveys and a well-coordinated network of astronomers worldwide to really capture the early phase of a supernova. Without data in its infancy, we could not have concluded that the explosion must have originated in the collapsing core of a massive star with an envelope about 500 times the radius of the sun."