Science Byte: on asteroids and comets

Written by Marie Brown

Asteroids and comets, just two similar varieties of objects hurtling through space, it is no wonder the terms so often get confused. There are, however, major differences between these celestial bodies.

Firstly, asteroids and comets have very different compositions; whilst asteroids consist of metals and rock, comets are made up of ice, dust, rocky materials and organic compounds. It is this ice which causes comets to have a brilliant glowing vaporous tail, caused by the sun’s rays warming the comet’s icy surface. Incidentally, the tail of a comet will always point towards the sun. Asteroids have low ice contents, and so it is rare to see one with such a tail.

Both asteroids and comets can be found orbiting the sun. The majority of asteroids orbit within the asteroid belt between Mars and Jupiter, whilst comets have a much larger orbit; some comets travel light years in a single orbit. Most asteroids group together in belts; ‘the asteroid belt’ sits between Mars and Jupiter and is where the majority of asteroids in our star system orbit.

What most of us really care about however, is whether or not we can see them from the earth. The answer is yes to both. The long tail of a comet can, on occasion be spotted in the night sky. An asteroid can leave a similar glowing streak above us, as it burns up in the atmosphere, creating what is often thought of  as a “shooting star”.

About the author

Marie Brown

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