A supernova is a powerful explosion that occurs at the end of a star's life cycle, resulting in the release of a massive amount of energy and the creation of new elements.
Supernovae are formed when a massive star runs out of nuclear fuel and can no longer support its own weight. This causes the star to collapse and then explode, releasing huge amounts of energy.
The first supernova was observed in 185 AD by Chinese astronomers. It was recorded in the Book of Later Han and is now known as SN 185.
The first supernova was significant because it was the first recorded observation of a supernova and helped scientists understand the life cycle of stars. It also showed that stars are not eternal and can undergo dramatic changes.
Supernovae that occur within a certain distance from Earth can potentially be dangerous due to the high levels of radiation and particles they emit. However, there are currently no known supernovae that pose a threat to Earth.