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Because of the crescent Moon this year's Perseid meteor shower should put on an impressive display between August 10 and 15 reports Sky and Telescope. The Perseids are one of the most of the dependable annual meteor showers and this year's is expected to have one or more meteors every minute at its peak on August the 12th.
Meteor showers are produced when the Earth crosses streams of debris formed by dust grains ejected from comets. Heating by the Sun of the nucleus of a comet causes its ice to turn to gas which forms a tail which can be millions of kilometres in length. Dust particles are carried along with the gas but eventually separate to form a dust tail that trails along behind the comet. Eventually the dust becomes spread out over the entire path of the comet to form a stream. The bright streak of meteors are produced by dust particles in the stream burning up as they sleet down through the atmosphere and virtually nothing remains to reach the Earth's surface. The peak of a meteor shower occurs when the Earth encounters the densest portion of the stream and because the dust particles in the meteor stream are all moving in more or less the same direction they appear to radiate from a single point in the sky (known as the radiant point).
The Perseids will be best seen from the northern hemisphere and have a radiant point between the constellations of Perseus and Cassiopeia which will be low on the horizon just before dawn.
More info: Sky and Telescope
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