The annual Orionids meteor shower peaks this year on October 21st but unfortunately a 93% lit waning gibbous Moon will significantly interfere and reduce the number of meteors visible. Generally regarded as a strong shower, the Orionids or Orionid meteor shower is active between October 2nd and November 7th although most activity is on the peak date or a few days before or after it. In the past, rates of up to 70 per hour have been observed but normally the shower is not so active; a figure between 20 and 25 is more the norm at the moment.
The Orionids parent comet is the most famous of all, Halley's Comet (1P/Halley). There are two annual meteor showers associated with Halley's Comet, the Eta Aquariids shower that occurs in May and the then the Orionids. Of the two the Orionids is by far the more prolific.
Although Halley is now in the outer solar system and will not return close to Earth until 2061, it's worth remembering that Orionid meteors result from particles leftover from the comet. Every observed Orionid is actually a small part of the famous comet streaking through and subsequently burning up in the Earth's atmosphere.
The radiant of the Orionids is located in the north-eastern part of the constellation Orion, not far from the Gemini border. Since Orion straddles the celestial equator, the Orionids are one of the few annual showers that are well placed for observation from almost anywhere on Earth, except the polar regions.
What to expect in 2013?
The major problem for 2013 is the Moon, it's almost full and will badly interfere. However, the shower is usually reliable with some bright meteors. They are fast moving and hit the atmosphere at very high speeds of 235,000 km/hour (145,000 miles/hour). At this velocity they will streak through the sky.
As with all annual meteors showers, it's best not to look directly at the radiant itself, as meteors can appear many degrees from it. A good idea this year is to try and position yourself in such a way that the Moon is out of view - for example behind a building or some trees - and then look towards the correct region of sky. This will give yourself the best chance of catching a few Orionids as they zoom by!
Orionids Data Table 2013
|Meteor shower name||Orionids|
|Meteor shower abbreviation||ORI|
|Activity||October 2nd -> November 7th|
|Peak Date||October 21st|
|RA (J2000)||6hr 20m|
|ZHR||20 to 25 (can vary between 20 and 70)|
|Notes||Most prolific meteor shower associated with Halley's Comet|
Comet 1P/Halley Data Table (at epoch February 17th, 1994)
|Classification||Halley-type comet (NEO)|
|Discoverer||Prehistoric, Edmond Halley first recognised the periodicity|
|Aphelion distance (AU)||35.0823|
|Perihelion distance (AU)||0.58598|
|Semi-major axis (AU)||17.8341|
|Orbital period (years)||75.3175|
|Longitude of ascending node (degrees)||58.4201|
|Last perihelion||February 9th, 1986|
|Next perihelion||July 28th, 2061|
|Notes||Halley's comet, the most famous of all comets|