What's a meteor shower?

Meteor showers occur when the Earth encounters the debris fields left behind by visiting comets. As comets travel through space and near the sun, small particles of rock and metal break off, leaving fragments in their wake like a trail of crumbs.

These fragments are called meteoroids, and when they enter the Earth's atmosphere, they burn up because of friction and can glow for several seconds, lighting up the night sky.

If a part of the meteor survives the trip through the atmosphere and hits the ground, it's a meteorite. But that is a rare occurrence.

Meteoroids are usually pretty small. According to NASA, most meteors range in size from one millimetre to one centimetre in diameter, barely more than a grain of sand. The light they produce while burning up, however, is very intense and can be seen from hundreds of kilometres away.

Many people call these celestial fireworks "shooting stars," but they really don't have anything to do with stars at all.

Why are they so bright?

The intense light of a meteor breaking up is created when a dust particle hits air molecules in the Earth's atmosphere. The impact vapourizes the outer layers of the meteor, leaving a trail of iron, magnesium and sodium.

When this trail of molecules makes subsequent impact with air molecules, the electrons are "bashed" out of their regular orbit with their corresponding nuclei, creating light in the process.

The colour of light produced depends upon the composition of the meteorite. Iron particles produce yellow light; sodium particles produce orange-yellow light; magnesium produces a blue-green light and silicon atoms produce red light.

How are they named?

The debris from a comet travels in parallel lines, and when that hits the Earth's atmosphere, it appears to originate from a single point, just as parallel train tracks appear to converge to a single point.

The Perseids, for example, get their name from the constellation Perseus, because that is where the shower appears to originate. Similarly, November's Leonids appear to come from within the constellation Leo, and December's Geminids appear to originate from within the constellation Gemini.

http://www.cbc.ca/technology/story/2...-perseids.html