The Orionids are the second annual meteor shower of the year that is caused by Earth passing through dust released by Halley's Comet, the first being the Eta Aquarids. As their name indicates, the Orionids have their radiant – the point from which they appear to radiate – in the constellation Orion.
The Orionids usually start on October 15 and end on October 29, and reach a peak during the morning hours of October 20–22. In the northern hemisphere, the maximum rate seen is typically around 20 meteors per hour, and in the southern hemisphere about double that rate. The maximum can last two or three nights.