Xiang-Dong Li

Astronomers have finally found compelling evidence that black holes are indeed born in supernovae. Around the black hole SS 433, a shell of hot gas is visible — like cooling steam from a massive star explosion that thundered 20,000–30,000 years ago.

In 1181, Chinese astronomers spotted a flash — likely the merger of two white dwarfs. Modern observations of the Pa 30 nebula barely pick up a radio signal. This means the explosion’s energy was extremely low, or particle acceleration works differently. The discovery forces us to rethink the nature