The Orionids meteor shower is the second shower that the Earth experiences each year from the long-orbiting Halley’s comet. Halley’s is not only responsible for the Eta Aquarid shower we experience each spring, but also for the Orionids that we encounter in the middle of October.
Lasting from approximately October 15th to October 29th, the Orionids are a moderate shower that primarily only produce easily visible meteorites during it’s peak days which generally fall between the 20th-22nd of October. For the most part, meteors from the shower are barely even detectable during most of the time that we are passing through the dust belt. Even at it’s peak, the Orionids shower tends to only produce a maximum of 20-40 meteors per hour depending on where you are located.
Typically, the Orionids shower is best viewed from the southern hemisphere. In this location, observers are often able to view up to 40 streaks per hour during the showers peak period. In the northern hemisphere, observers generally see no more than 20 streaks per hour, though typically less than that.
The interesting thing about the Orionids shower is that it’s peak time is very unpredictable. Though the shower generally only peaks between the 20th-22nd, in the past this peak period has occurred often days earlier or later than predicted. There have also been occasions that the peak period has lasted for much longer than usual, sometimes for up to six days. During this time the maximum number of meteors seen is often higher, though it is normally no more than 35-40 streaks per hour.
Many astronomers attribute this irregular pattern to the shape of the dust belts that cause the Orionids, which are twisted like a rope and have varying levels of density. As we pass through the dust belt each year, we encounter areas with different density levels which cause the results of the shower to change from year to year. Having observed the meteor shower since it’s discovery in 1839, astronomers have noted that we seem to experience the maximum peak period of the shower approximately 10-25 years before Halley’s comet passes close to the Earth, as there is a much higher density of debris in that particular part of Halley’s orbit.
The Orionids are best viewed in the early morning hours after midnight with the best activity closer to dawn. The radiant of the shower is the constellation of Orion, which can easily be found in the night sky by locating Orion’s belt, a cosmic formation most stargazers are familiar with. The radiant does fall more between the constellations of Orion and Gemini however, so if you train your eyes towards those locations in the sky you should have no problem in locating the Orionids shower when it occurs.
Christopher L. Shelby, M.D.