What are shooting stars?

Have you ever looked up at the sky and a bright streak of light? These are known as shooting stars but despite their name these are not stars at all but instead meteoroids (most are smaller than a grain of sand).

Meteoroids are small crumbs of dust that fall off of asteroids or comets as they travel through space, some intersect with earths orbit enter the atmosphere rubbing against air particles as they do which creates friction and heat. The heat vaporizes them resulting in the coloured streaks of light you see.

They can be a range of different colours depending on what they are made of, for example sodium would make a yellow-ish coloured streak and copper would create a a green streak. The usual composition of meteoroids is nickel which makes a greenish streak.

During most of the year you will see few shooting stars a night but during other times the earth passes through debris fields left from comets resulting in meteor showers where a lot more meteoroids enter the atmosphere. Numbers vary but the median is 60 per hour with perfect conditions and minimal light pollution.