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The Perseids is one of the most prominent and prolific meteor showers visible in the northern hemisphere. The meteors are caused by the Earth passing through the debris of an old comet, Swift-Tuttle, and small particles of debris being drawn into the Earth's atmosphere where they then burn up. The particles will mainly be the size of small grains of sand with some larger particles which give rise to the larger brighter 'shooting stars'.

The shower is given the name 'the Perseids' simply because if you plot the paths of the meteors against the background sky, they appear to have come from the constellation Perseus. Of course, as on any other night, there may also be some non-related meteors, referred to as 'sporadics', which will come from completely directions.

Depending on the size of the particles, their speed and angle of entry and atmospheric conditions, the meteors can be of different brightness, different colours and different durations, with the odd 'fireball' thrown in for that occasional 'WOW' moment, if you are lucky enough to be looking in the right place at the right time.

The Perseid meteor shower occurs every year between 17 July and 24 August, with a sharp peak typically seen around 11-13 August. The average velocity of the meteors is 59 kms/sec with an average apparent magnitude of 2.2 and the zenith hourly rate is about 100 per hour, although not all of these will be visible.

Observing the meteors can be done very easily with no equipment needed - just a comfy chair or sunlounger, a blanket and a warm drink. If you want to get a bit more scientific you might want a notebook or clipboard with a constellation map showing Perseus, to record the number, direction, brightness, colour, apparent speed and duration of the meteors you see. Of course, it is also possible to photograph meteors and some people will take a camera with a wide-angle lens, (or even a video camera) and set it running taking lots of 20 - 30 second exposures, which can later be combined to (hopefully) show meteor images spreading out from the radiant in the constellation of Perseus.

A more comprehensive guide has been published by the Sky at Night Magazine: HERE

Here is a link to another guide produced by NASA: HERE

Article by Graham Finch

Mid-Kent Astronomical Society
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