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The earth's orbit takes it through clouds of space particles, known as meteoroids. These particles seem to originate from comets, normally, or occasionally asteroids. The tails of comets contain dust particles If a meteoroid enters the earth's atmosphere and starts to burn, it is known as a meteor. Meteors are usually just tiny particles, the size of a grain of sand. They enter our atmosphere at speeds of up to around 45 miles per second, becoming visible at an altitude of about 55 miles, see diagram below. The actual phenomenon that we know as a meteor is terrestrial in nature, more than astronomical, as the light seen is produced by atmospheric interaction (friction).
The vast majority of these meteors burn up without reaching the surface of the earth. Occasionally, a relatively large meteor will make it to the earth's surface, when it becomes known as a meteorite. Meteorites are normally small (fit in the hand sized) either mainly silicon based rock or metalic, iron-rich lumps, or a mixture of both. Throughout history there appears to have been occasional large meteor strikes, producing craters in the earth.
Meteors are spotted sporadically throughout the year. However, on and around certain dates, we are showered by larger numbers of meteors as we pass through debris clouds. Unsurprisingly, these are known as meteor showers! The major meteor showers are named according to the region of space that they appear to radiate from.
The major meteor showers visible from the UK are listed in the table below, together with some useful information. The peak dates are approximate, as there is a slight annual variation due to leap years. In general, meteor observation is most fruitful in the early hours of the morning, when the observer is facing the direction that the earth is travelling in its orbit, hence maximising the possibility of impact. However, there are some exceptions to this, so I have added a `Best Viewing Time' column to the table.
Some interesting facts about the major meteor showers listed below:
1. The Perseids and the Geminids are USUALLY the two showers that are the best and brightest of all of the showers.
2. The Quadrantids and the Geminids are thought to be debris from asteroids. All of the others originate from passing comets.
3. Occasionally, the Leonids can produce spectacular bursts of meteors, eclipsing all of the other showers of the year.
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