* A supernova: These are extremely bright explosions of dying stars, but they are rare events. If a supernova happened in Cassiopeia, it would be major news and widely reported.
* A nova: These are less powerful than supernovae, but still involve a dramatic brightening of a star. They are more common than supernovae, but still not frequent enough to be a regular occurrence.
* A variable star: Many stars in the sky change their brightness over time. Perhaps you're thinking of a variable star in Cassiopeia that has become unusually bright.
To help me identify what you're looking for, please tell me:
* When did you hear about this "new star"? Was it a recent discovery?
* What kind of star did you think it was? Was it super bright, or just noticeably brighter than usual?
With more information, I can help you find out more about what you're looking for!
