Orionid Meteor Shower From Halley's Comet Peaks Ahead of Rare Halloween Blue Moon

The Orionid meteor shower is set to peak tomorrow night ahead of a rare Halloween blue moon later this month.

The American Meteor Society (AMS) predict that the shower will be most active on the night of October 20-21, when up to 20 meteors per hour could be visible from areas free of light pollution.

The Orionids are a medium strength meteor shower that begin in October every year as the Earth passes through debris left behind by Halley's Comet, which is visible from our planet every 75-76 years.

When this happens, pieces of debris enter the Earth's atmosphere at speeds of up to around 150,000 miles per hour.

In the process, they burn up due to the effects of friction with the air, generating the fleeting streaks of light visible from the ground which are known as meteors or "shooting stars."

The Orionids have been known to produce more than 50 meteors per hour in exceptional years, but usually, maximum rates at the peak hover between 10 and 20 per hour.

The moon will appear just 23 percent illuminated on the night of the peak so skies should be relatively unimpeded by moonlight, although cloudy weather in your location could hamper views.

Like all meteor showers, the Orionids appear to originate from a particular point in the sky known as the radiant, which in this case can be found close to the constellation Orion.

Orionid meteors are not visible until after 10 p.m. because the radiant does not rise above the eastern horizon before then. The best time to see them is from 1 a.m. until dawn, the AMS said.

The peak of the Orionids comes just over a week before a rare Halloween blue moon is set to appear in the skies.

The term "blue moon" has nothing to do with the moon's color. Instead, it refers to any full moon that is the second to appear in a single calendar month.

There has already been one full moon this month—the one that appeared on October 1—and so this Halloween's full moon will be a blue moon.

Blue moons occur on average every two-and-half to three years. Full moons on Halloween only occur once every 18-19 years and the next one won't be visible until October 2039.

The blue moon on Halloween will technically look most full at 10:49 p.m. ET on October 31, although to most people, it will appear full for a day either side of this time.

Orionid meteor shower
Orionid meteor in 2012 over Shenandoah National Park, Virginia. The Orionid meteor shower is set to peak on the night of October 20-21. Michael Orso/Getty Images