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Meteor Showers

Meteor showers occur when the Earth collides with a collection of particles also orbiting the Sun. It is usually believed that these particles of ice and dust are the remnants of comets that once passed through the inner solar system. When these meteoroids enter the Earth's atmosphere, friction with the air causes them to heat up and glow. This is what causes meteors, the brief streaks of light that you see in the sky. Most meteoroids burn up completely in the atmosphere but occasionally one survives to actually hit the Earth. This object is then termed a meteorite. Meteorites are subdivided into two main categories: stones (stony meteorites) and irons (iron-nickel meteorites).

Not all meteorites are pieces of comets. A number of meteorites have been found in the Antarctic which have been traced back to our neighbouring planet Mars! Some scientists even believe that a few of these objects contain microfossils of ancient Martian bacterial life. Larger meteorites may be pieces of asteroids. Many people believe that the great extinction at the end of the Cretaceous period was caused by a large asteroid hitting the Earth. The resulting dust cloud then cooled the Earth and caused many species to die out, including the dinosaurs.

Meteors can be seen on any clear night although they are usually more prevalent after midnight. If you are lucky, you might glimpse a sporadic bolide or fireball. However, your best chance for seeing meteors is during a meteor shower. These are not confined to a single night but are spread out over a period of days or weeks with a peak at a given time. An optical illusion makes it appear that all the meteors in a shower are emerging from a single point called the radiant. However, the meteors are actually travelling in parallel. As an analogy, look at a set of straight railroad tracks. The tracks are parallel but the farther into the distance you look at them, the closer they appear to get until they converge. In the same way, perspective makes it appear as if meteors in a shower are originating from a common point.

Here is a list of some of the major meteor showers. A three-day span is given for the peak times of the showers due to the unpredictable nature of this phenomenon.

Name	Dates	Approximate Peak	Best Views	Appearance	Parent
Quadrantids	early January	2-4 January	northern hemisphere	moderately bright, medium speed	unknown but may be the same as for the Delta Aquarids
Alpha Centaurids	late January to mid-February	6-8 February	southern hemisphere	fast and bright with many trains
Gamma Normids	late February to mid-March	12-14 March	southern hemisphere	fast and bright, and mostly white and yellow
Lyrids	mid-April to late April	21-23 April	either hemisphere	fast and bright with some trains	C/1861 G1 Thatcher
Pi Puppids	mid-April to late April	22-24 April	southern hemisphere	bright but very slow in speed	Comet 26P/Grigg-Skjellerup
Eta Aquarids	mid-April to late May	4-6 May	either hemisphere	fast and bright with many trains	1P/Halley
Delta Aquarids (south)	mid-July to mid-August	29-31 July	either hemisphere	medium speed but faint	unknown but may be the same as for the Quadrantids
Perseids	mid-July to late August	11-13 August	northern hemisphere	fast, bright, and colourful with many trains	109P/Swift-Tuttle
Alpha Aurigids	late August to early September	31 August to 2 September	northern hemisphere	fast and bright
Delta Aurigids	mid-September to mid-October	27-30 September	northern hemisphere	fast but faint
Draconids	early October to mid-October	7-9 October	northern hemisphere	slow, faint, and yellow in colour	21P/Giacobini-Zinner
Orionids	early October to early November	20-22 October	either hemisphere	fast and sometimes bright with some trains	1P/Halley
Leonids	mid-November	16-18 November	either hemisphere	very fast and very bright with most leaving trains	55P/Tempel-Tuttle
Alpha Monocerotids	mid-November to late November	20-22 November	either hemisphere	very fast with some quite bright
Phoenicids	late November to early December	5-7 December	southern hemisphere	very slow and faint
Puppid-Velids	early December to mid-December	6-8 December	southern hemisphere	average speed and brightness
Geminids	mid-December	13-15 December	either hemisphere	average speed but very colourful	3200 Phaeton
Ursids	mid-December to late December	21-23 December	northern hemisphere	average speed and faint	8P/Tuttle

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