Great Comet

A Great Comet is a comet which becomes particularly bright and it is very spectacular to be noticed by a casual observer. A great comet usually (but not always) appears about every decade.

Predicting whether a comet will become a great comet is notoriously difficult, as many factors may cause a comet's brightness to depart drastically from predictions. Broadly speaking, if a comet has a large and active nucleus, will pass close to the Sun, and is not obscured by the Sun as seen from the Earth when at its brightest, it will have a chance of becoming a great comet.