I.

Introduction

Novae and Supernovae (Latin, stella nova, “new star”), two kinds of explosive event that take place in some stars. A nova is a star that suddenly increases greatly in brightness and then slowly fades, but may continue to exist for some time. A supernova exhibits the same pattern of behaviour, but the explosion destroys or profoundly alters the star. Supernovae are much rarer than novae, which are observed fairly frequently in photographs of the sky.