- Written by Nadia O'Carroll
Shooting stars’ trail of light is produced because meteoroids hit the Earth’s atmosphere at high speeds, a minimum of 11.2 km/second. As they collide with the air molecules, the ram pressure causes the surface of the particle to glow white hot as it melts and is transformed into gas, and a large volume of the surrounding air also becomes electrically charged.
Although shooting stars may appear to be large objects, most pieces of cosmic debris are very small (typically 1mm). A piece of grit the size of a grain of sand will produce a shooting star, a pea sized piece of debris will cause a spectacular blaze of light and a piece of debris larger than an apple will cause a fireball.
The dust and particles that cause shooting stars are mainly the debris left by the trail of comets as they orbit the Sun. As the Earth orbits through this debris trail, multiple meteors may be seen and these are called meteor showers. By calculating when the orbit of Earth intersects with the trail of the orbit of a comet, it is possible to predict when an annual meteor shower will occur. The annual meteor showers are named after the constellations, which are in the same region of the sky as the meteor showers. One of the most spectacular meteor showers originates from the tail of the Swift-Tuttle comet. This meteor shower is visible in August, and is called the Perseid meteor shower, after the constellation Perseus.
When thousands of meteors are produced every hour, the phenomenon is called a meteor storm. The Leonids meteor shower occurs every November and is usually less active than the Perseids. However every 33 years the Leonids produces a meteor storm, in 1933 and 1966 these were spectacular events, but the meteor storm of 1999 produced far less meteors than expected.
The best time to see shooting stars is a few hours before dawn. However if we want to continue to see these spectacular cosmic sights, we have to keep light pollution in check, so if we minimise obtrusive outdoor lighting we can save on the power bills and preserve our view of the amazing night sky.