What's the Difference Between a Comet, an Asteroid and a Meteorite?

Question posed by Emily FG.

You can find out the difference between a comet and meteor in this post, and a meteorite is just what we call meteors after they have landed.

What's not covered in that post is what an asteroid actually is. So...


What's an Asteroid?

Asteroids are lumps of rock and/or metal that are in direct orbit around the Sun (i.e. they're not in orbit around anything else). Like so many astronomical objects, asteroids are very loosely defined- most of the moons of our solar system would classify as asteroids if they weren't in orbit around a planet, although the bigger ones may come under the heading of 'dwarf planet' instead.


What's the Difference between Comets, Asteroids and Meteorites?

Comets are:

• Big balls of dirty rock and ice in orbit around the Sun. They have great big tails when they're close to the Sun and can hang around in the sky, when we're lucky enough to see one, for weeks.

Asteroids are:

• Big lumps of rock and metal in orbit around the Sun. They don't show up all that often, and if you see one with your naked eye you'll probably be too busy screaming and running away to take much notice.

Meteorites are:

• Meteors that have landed. Lots of them do this, but you're unlikely to find one because picking one out amongst all the Earth rocks is difficult to do unless you live in Antarctica. Meteors are meteoroids that have entered the Earth's atmosphere, and are often known as 'shooting stars'. You're lucky if you see one because most visible ones last for a fraction of a second. Meteoroids are lumps of rock that are smaller than asteroids and not in direct orbit around the Sun- they're generally heading towards another body. Good job they're not too big, then.