Great Comet

A Great Comet is a comet that becomes exceptionally bright. There is no official definition; often the term will be attached to comets that become bright enough to be noticed by casual observers who are not actively looking for them, and become well known outside the astronomical community. Great Comets are rare; on average only one will appear in a decade. While comets are officially named after their discoverers, Great Comets are sometimes also referred to by the year in which they appeared great, using the formulation "The Great Comet of...", followed by the year.