great comets

Great comets are comets that become exceptionally bright and visible to the naked eye, often developing spectacular tails that stretch across the night sky.

Unlike most comets, which require telescopes to observe, great comets appear perhaps once or twice per decade and become memorable public events.

Their brightness depends on a combination of the comet's size, how close it passes to the Sun, and how close it comes to Earth.

Halley's Comet was a great comet in 1910 but only moderately impressive in 1986.