It came from outer space...

25 December, 2011

A comet: close-up of the comet NEAT taken from Kitt Peak Observatory.
A comet: close-up of the comet NEAT taken from Kitt Peak Observatory.
Image: NASA
Source: NASA (courtesy of

Question: What's the difference between a comet, an asteroid, a meteoroid, a meteor and a meteorite?

Answer: The differences between comets, asteroids, meteoroids, meteors and meteorites can appear subtle, but they are distinct objects.

Comets are the leftovers from the formation of the solar system over 4 billion years ago; they are the bits and pieces that never managed to come together to form a planet, but like planets they orbit our Sun.

Because of their deep orbits in the colder reaches of space, comets are a mixture of ice, dust and rock. When comets travel close to the Sun, their icy layers melt away releasing dust and gas, which gives the comets their characteristic tails.

Asteroids are similar to comets in that they are also leftover pieces from the formation of the solar system that orbit our sun. However, asteroids are rocky or metallic in composition rather than icy. Most of them are found in the Asteroid Belt, between Mars and Jupiter.

Chunks from asteroids and comets are collectively called meteoroids. Meteoroids are essentially space dust - dust that may have been created by a collision between asteroids in the Asteroid Belt, or left behind when a comet travelled near to the Earth. When the Earth moves through a particularly dusty region, we get to experience a meteor shower.

As a meteoroid travels through Earth's atmosphere it heats up, producing a streak of light. It is then called a meteor (or a 'shooting star').

If a meteor manages to survive its journey though the atmosphere and makes contact with the Earth, it is then called a meteorite. Every day, tons of meteoroids travel through our atmosphere, without us even noticing.

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