Saturday, October 17, 2009

Welcome the Orionids

No, I'm not talking about an alien race coming to Earth, though the Orionids are extra terrestrial. This weekend marks the return of the Orionid meteor shower. The Orionids are one of the best annual showers. The others are the Geminids in December and, the king of the annuals, the Perseids in August.
This shower is caused by dust from periodic Comet Halley (1P/Halley), which last came by in 1986. Halley is also responsible for the Eta Aquarid shower in early May. Under very dark skies, meteors from the Orionid shower actually may be visible from the beginning of October through the first week of November. The Orionid shower is very reliable, giving consistent rates each year. Over the duration of the shower the hourly rate gradually rises and then gradually drops off. The maximum lasts from about October 19 through 23, with the peak around the October 21/October 22 (Wednesday night/Thursday morning. At its peak, the shower is projected to produce 25 to 30 meteors per hour. The meteors will appear to radiate from a point in the sky between the constellations Gemini and Orion (RA 06hrs 20min, Dec +15°). This radiating point is called, appropriately enough, the radiant.
This year, the peak falls around a new moon, which sets not long after sunset. This will improve the chances of a good show even in moderately dark skies.
The Orionid shower radiant rises at about 11 p.m. local time and the best viewing should come after local midnight. To best view the Orionid shower, find a reasonably dark location away from city and neighborhood lights. Bring along a lawn chair, deck chair, or even a blanket if you wish. Also bring along a jacket and maybe a warm beverage. You might be amazed how cool it gets when you are sitting or lying still in the darkness for hours at a time. Once you are situated at your observing site, allow enough time for your eyes to adapt to the darkness--about 15 or 20 minutes. This will permit you to see fainter objects. Binoculars are not necessary. Just slowly scan the sky with your own eyes. And enjoy the show!

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