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    Meteors are often known as 'shooting stars'. However, this description could hardly be further from the truth! They're absolutely miniscule compared to stars and the only reason they're visible is because they're so close to Earth.

    What is a Meteor?

Meteorite entering Atmosphere Credit: NASA/ESA

    Meteors (from the Greek word 'Meteoron') are the streaks of light that are made when meteoroids, ie dust particles and rock fragments floating around in space, enter the Earth's atmosphere. Thousands of such meteoroids come hurtling into the Earth every day, generally at very high speeds, creating these streaks of light which can be seen by the naked eye in a clear, cloudless night sky.

    The vast majority of meteoroids which enter the atmosphere are burned up by the intense heat created by the friction between them and the atmosphere itself at a height of 55-65 miles above our heads, thus creating meteor streaks. Luckily for Meteor-watchers therefore, very few meteoroids are large enough for a sizeable chunk of them to make the journey to the Earth's surface. Those that do crash into the Earth's surface are called Meteorites, and if they touch down on land, will create a meteorite crater, or 'impact crater'.

    Craters and Origins of Meteoroids

Barringer Impact Crater, Arizona Credit: USGS/D.Roddy

    There are a number of Meteor craters on the Earth's surface, created through the ages by meteorites large enough to reach the Earth with a considerable mass remaining. One of the most recognised is the descriptively named 'Barringer Impact Crater' in Arizona (see image), created 49,000 years ago when the Barringer meteorite (estimated to have been roughly 40 metres in diameter upon impact) slammed into Arizona at 11km/s, creating this 1.2km wide, 183 metre deep crater.

Meteoroids generally come from within the Solar System, as far as we know. By analysing their composition, clues can be gleaned as to where they originated from. Such analysis has shown that some meteorites show a very similar composition to the Earth itself and the Moon, an indication that they may have originated from the moon. Others bear some resemblance to asteroids,

Leonid Meteor Shower from Space Credit: NASA/ARC

others to comets, and 12 meteorites found in Antarctica are even believed to have originated from the planet Mars!

    Meteor Showers

    Although they can be seen against a clear night sky the whole year round, Meteors can be seen to increase sharply in number at certain times of the year; such occurances may be referred to as 'Meteor Showers'. One of the most visible and regularly occurring meteor showers, the 'Perseid' meteor shower, takes place around the day of 'St Laurence', on the 12th August, give or take a day or two, depending on the year. During such periods, the Earth is passing through the tail left by a comet as it cut through the path of the Earth's orbit hundreds of years ago. The Earth moves through the tail, made of dust and other small fragments, and the particles which the Earth 'bumps into' become meteors.

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