<human>:  Why do the Halley’s Comets have such a long orbital period?
<bot>: Halley’s Comet has an orbital period of 76 years. This is due to the fact that it is a periodic comet, meaning that it orbits the sun in a very similar pattern every 76 years. The orbital period of a comet is defined as the time it takes for a comet to complete one orbit around the sun. The orbital period of a comet is related to its size, since smaller comets have shorter orbital periods.