1. The explosive death of a star, which temporarily attains a brightness of 100 million suns or more, so that it can shine as brilliantly as a small galaxy for a few days or weeks.
2. A stellar explosion which increases the luminosity of the star to many thousands of times brighter than a nova.
3. The sudden, temporary and enormous increase in brightness of a star, resulting from the blowing off of most of its constituent material during its destructive process.

Such an event occurs for stars only about six times more massive than the sun, the result being a white dwarf.

The gas cloud ejected by the explosion of a supernova that spreads out into space, perhaps for millions of years.

During this time, the stellar remnants radiate huge amounts o energy, not only as visible radiation, or light, but also as X-rays and radio waves.