Orionids

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An Orionid meteor streaking across the sky below the Milky Way and to the right of Venus. The zodiacal light can also be seen in the image.

The Orionids is the name of the most prolific^{[citation needed][clarification needed]} meteor shower associated with Halley's Comet. The Orionids are so-called because the point they appear to come from, called the radiant, lies in the constellation Orion Orionids are an annual meteor shower which last approximately one week in late-October. The peak of the 2009 Orionid meteor shower will occur around October 21, 2009 and produce from 20-25 meteors per hour in the Northern Hemisphere, and double this amount in the Southern Hemisphere.^[1][2] Japanese scientists say that due to the comet going through old debris producing elevated displays of activity lasting several nights, the dates 21, 22 and 23 should be good viewing.^[3] Bill Cooke of NASA's Meteoroid Environment Office related that in the last three years, the Orionids meteor shower has produced more that 60 meteors per hour creating a "fireworks" show visible without telescope or binoculars.^[4] The 2006 and 2007 meteor showers were spectacular meteor showers producing over 50-70 meteors per hour (Zenithal Hourly Rate) over two to three nights with unusually bright meteors in 2006.^[5] The meteor shower is sensational in comparison to the Leo Minorids meteor shower which climaxes on October 23, 2009 with 2 meteors per hour. "There are no guarantees in meteor work ... observers should be alert as often as conditions allow throughout the shower, in case something unexpected happen."^[6]

[edit] History

Meteor showers first designated "shooting stars" were connected to comets in the 1800s.^[7] E.C. Herrick made an observation in 1839 and 1840 about the activity present in the October night skies. However A.S. Herschel produced the first documented record which produced accurate forecasts for the next meteor shower.^[8] The Orionid meteor shower is produced by the well-known Halley’s Comet, which was named after the astronomer Edmund Halley and last passed through the inner solar system in 1986 on its 75-to-76-year orbit.^[9] When the comet passes through the solar system, the sun melts some of the ice which allows rock particles to break away from the comet. These particles continue on the comet's trajectory and appear as meteors or "falling stars" when they pass through Earth's upper atmosphere.^[7][10] Halley's comet is also responsible for creating the Eta Aquariids which occur annually in May.^[10]

• This meteor shower may give double peaks as well as plateaus, and time periods of flat maximums lasting several days.^[8]

[edit] Meteor shower and location

Map of the night sky showing the constellation Orion and Betelgeuse and a portion of the Gemini constellation

The radiant of the Orionids is located between the constellations Orion and Gemini (in the south-eastern sky before dawn, as viewed from mid-northern latitudes.^[14][15] The most active time of the meteor shower was stated by Telegraph.uk.co to be in the early morning of October 21, 2009 6 a.m. Eastern Standard Time in the United States or 11 a.m. in the United Kingdom. Tweets and user news articles were shared on Social networking and micro-blogging services such as Twitter and Yahoo! Buzz. Photos and videos of the event were posted on photo and video sharing websites such as YouTube and Flickr.^[16] Universe Today reported that the meteor shower arrived at 140,000 miles (225,308 km) per hour on the morning of the 21 when showing was predicted to be at its height, however compared to previous showers in years past, the trail of 2009 appeared narrower without branching out.^[17] Cooke, found that the originating points of 30 meteors were from withing a very small area of the Orion constellation even though observers observing the small meteor "Halleyids" at Alabama's Space Flight Center saw steaks radiating in all directions with the naked eye.^[18] Observers can follow the meteor shower over consecutive nights then fill out a report form of their visual observations of the Orionid rates at the International Meteor Organization where the results are compiled into the automated Zenithal Hourly Rate ZHR graph named Orionids 2009: visual data quicklook.^[19]

The meteor shower is expected to last a few days; Orionids meteor activity is predicted to last between Sunday October 18, to Sunday, October 25, 2009. Some observers may be treated to a fireball or Bolide.^[15][20] Observers watching the meteor shower from the Southern Hemisphere will see double the amount of meteors per hour than those observers in the Northern Hemisphere who may only see 20 meteors per hour. Annual nightly viewing dates vary, and the meteor shower may peak at various times due to yearly fluctuations.^[2][8] Japanese meteor scientists Mikiya Sato and Jun-ichi Watanabe advised that the meteor shower will last several nights around the peak producing broad bands of good displays, so the nights of the 22 an 23rd should also produce rich results. "We have found that the [elevated activity of 2006] was caused by dust trails ejected from 1P/Halley in 1266 BC, 1198 BC, and 911 BC. The debris that hit Earth in 2006 was rich in large fireball-producing meteoroids."^[3]

[edit] Gallery

Orionid		Two Orionids and Milky Way	Multi-colored Orionid
	The brightest meteor, a fireball, leaves a smokey persistent trail drifting in high-altitude winds, which is seen at the right-hand side of the image.

[edit] See also

• Meteor showers
• List of meteor showers

[edit] References

[edit] External links

• Spaceweather.com: 2009 Orionid Meteor Shower photo gallery: Page 1
• realclearwx.com: 2009 Orionid Meteor Shower Photos & Video