<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 because it is a periodic comet, which means that it is not a single object but rather a collection of small objects that periodically orbit the sun. This is a common trait among comets, which makes them interesting to study because they are thought to be leftover material from the formation of the solar system.