Orionid Meteor Shower: Late October Peak of Debris From Comet Halley

Summary: The Orionid meteor shower offers a late October peak of debris from Comet Halley, and a planetary quartet joins 2015's Oct. 21 to 22 shooting stars.

45 minute composite shot during Orionid meteor shower, with Jupiter as diffraction spiked star (center), in skies over Sussex, northwestern New Jersey; Saturday, Oct. 20, 2012: jason jenkins, CC BY SA 2.0 Generic, via Flickr

Peaking in 2015 in the early mornings of Oct. 21 and 22, the Orionid meteor shower serves as one of two yearly reminders of Halley’s Comet, the most famous comet in the skies over Earth.

As with spring’s Eta Aquarids, which peak around May 5 to 6, the autumnal Orionid shower of shooting stars is occasioned by Earth’s passage through debris released by Comet Halley, officially designated as 1P/Halley, during the short-period comet’s 75- to 76-year circuit around the sun.

Typical of most meteor showers, the Orionids provide best viewing, for all time zones, in the early hours after midnight and before dawn. The moon, which is finishing its first quarter phase at 47 to 58 percent visibility, offers no competition in the early hours of Oct. 21 and 22 by setting in the late evening or, at the latest in some time zones, within or near the midnight hour. Orionid visibility ranges from the 85 degrees north latitude, which passes through the Arctic Ocean, and the 75 degrees south latitude, which passes through northern coastal Antarctica and the Southern Ocean.

depiction of Orion the Hunter constellation in ca. 816 illuminated astronomical manuscript, Leiden Universiteitsbibliotheek VLQ 79, known as Leiden Aratea: Public Domain, via Wikimedia Commons

In addition to impeccable parent body lineage, the Orionid meteor shower claims the prominent constellation of Orion the Hunter as namesake radiant, or apparent point of origin. Although not actually streaming from the globally visible constellation, Orionid shooting stars appear, from the perspective of Earthlings, to radiate from Betelgeuse, the distinctly reddish star that establishes the hunter’s upraised right shoulder. Known in astronomy as Alpha Orionis (shortened to α Orionis or α Ori), Betelgeuse shines as Orion’s second brightest star and as the night sky’s ninth brightest star.

The Orionid meteor shower peaks with unpredictable maximum rates, ranging in activity from medium to high strength. Normal peaks produce a maximum of 20 to 25 shooting stars per hour while exceptional peaks, such as occurred from 2006 to 2009, compete with mid-August’s Perseids for busy rates of 50 to 75 shooting stars per hour.

As with sibling Eta Aquarids, the Orionids feature swift movement. Orionid shooting stars attain velocities of 42 miles per second (66.9 kilometers per second). Speedy meteoroids tend to explode as fireballs, with an apparent magnitude brighter than that of Venus, the sky’s third brightest object. Striking Earth’s atmosphere at speeds of over 150,000 miles per hour (241,401.6 kilometers per hour), Orionid meteors occasionally trail their fireballs with incandescent streams of debris framed with smoky filaments shaped intriguingly by upper atmospheric winds.

As the Orionid parent body, Comet Halley continues to shed fresh debris that eventually replenishes the meteor shower. Comet Halley’s last perihelion, or closest orbital point to Earth, occurred Feb. 9, 1986. Its first perihelion in the 21st century is predicted to be reached July 28, 2061. While Comet Halley is a naked-eye comet with possible appearance twice in a human lifetime, the famous comet that framed the birth and death of American humorist Mark Twain (Nov. 30, 1835-April 21, 1910) strikingly bestows biannual reminders with spring’s Eta Aquarids and autumn’s Orionids.

To appreciate Comet Halley’s fiery remnants and to discover whether 2015 is a year of fireballs and maximum rates, viewers only need to position themselves comfortably underneath the cooperatively darkened skies of the early morning hours on Oct. 21 and 22. In the Southern Hemisphere, observers look toward the northeast for Orion and the Orionid meteor shower. Northern Hemisphere viewers watch the east-southeastern skies.

Amid clear, dark skies, the Orionid meteor shower does not disappoint. As a bonus, Jupiter, as well as Mars, Mercury and Venus, will all keep visible company with the Orionids in the predawn hours of Oct. 21 and 22.

Orionid meteor shower's parent body, Halley's Comet, crossing the Milky Way, Tuesday, April 8/Wednesday, April 9, 1986; NASA photo taken from Kuiper Airborne Observatory, C141 aircraft, New Zealand Expedition: NASA, Public Domain, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

45 minute composite shot during Orionid meteor shower, with Jupiter as diffraction spiked star (center), in skies over Sussex, northwestern New Jersey; Saturday, Oct. 20, 2012: jason jenkins, CC BY SA 2.0 Generic, via Flickr @ https://www.flickr.com/photos/jdub1980/8108045996/

depiction of Orion the Hunter constellation in ca. 816 illuminated astronomical manuscript, Leiden Universiteitsbibliotheek VLQ 79, known as Leiden Aratea: Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:LeidenArateaFOlio48vOrion.jpg

Orionid meteor shower's parent body, Halley's Comet, crossing the Milky Way, Tuesday, April 8/Wednesday, April 9, 1986; NASA photo taken from Kuiper Airborne Observatory, C141 aircraft, New Zealand Expedition: NASA, Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Comet_Halley.jpg

For further information:

Kronk, Gary W. “Observing the Eta Aquarids.” Meteor Showers Online.
Available @ http://meteorshowersonline.com/eta_aquarids.html

Marriner, Derdriu. “Eta Aquarids: Spring Meteor Showers Gift to Earth From Comet Halley.” Earth and Space News. Tuesday, May 5, 2015.
Available @ https://earth-and-space-news.blogspot.com/2015/05/eta-aquarids-spring-meteor-showers.html