The meteors from the Orionids come when Earth passes through the "trail" of dusty debris from comet Halley, or Halley’s Comet.
The material from Halley is hurled out dust and other particles from the comet when it gets close to the Sun and its heat evaporates some of the comet’s nucleus.
The brief streaks of visible light, sometimes called “shooting stars,” should be visible in the mid-northern latitudes for the Northern Hemisphere and the mid-southern latitudes for the Southern Hemisphere during the early morning hours before local dawn.
Look toward the southeastern sky in and around the constellation Orion and the constellation Gemini.
The center of the shower, what is called the comet’s radiant, will be just above Orion’s bright reddish-orange star Betelgeuse, which forms part of the shoulder of the constellation Orion.
Take a look at the sky map found at the Science at NASA’s website “The 2009 Orionid Meteor Shower.” [10/19/2009]
Page two continues with additional information on the Orionid meteor shower for 2009.
The show should last until October 25, with an average of about ten to twenty meters per hour; however, this number will be irregular from hour to hour.
For the past three years, the rate of comets per hour from the Orionids has been high, with sixty or more comets sometimes reported.
According to computer models made of the material within the Orionids, the rate of comets should also be very good this year.
In fact, Japanese meteor scientists Mikiya Sato and Jun-ichi Watanabe recorded the past three years of exception viewing for the Orionids.
They reported on the NASA website, "'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,’ they wrote in the August 2007 edition of Publications of the Astronomical Society of Japan.”
And, “In their paper ‘Origin of the 2006 Orionid Outburst,’ Sato and Watanabe used a computer to model the structure and evolution of Halley's many debris streams stretching back in time as far as 3400 years. The debris that hit Earth in 2006 was among the oldest they studied and was rich in large fireball-producing meteoroids.”
To check out the 2009 Orionid Photo Gallery of images already taken of the shower, go to SpaceWeather.com.