Asteroid, Meteoroid, Meteor, Meteorite, Comet: What’s the Difference?

This is one of my favorite topics of astronomy because people mix these up so often, and many people think they're all basically the same thing. Asteroids, meteoroids, meteors, meteorites, and comets are all quite different, and the differences between them can get confusing. So, I'm going to try to explain the difference between them as simply as possible.

Asteroid

An asteroid is a large rock floating in space. Well, it's not exactly floating in space, so much as it's hurling through space at 1,000's of miles per hour. And, an asteroid isn't really large compared to most other things in space; asteroids are relatively small, actually. Most asteroids are about a few meters in length and orbit between Mars and Jupiter. An easy way to remember what an asteroid is, is to think about Star Wars or Star Trek: when you're watching Star Wars or Star Trek, the large rocks drifting by their space ships are asteroids.

Meteoroid

You can think of meteoroids as tiny asteroids. They're usually not solid rock, like asteroids, but clumps of dust and debris. Meteroids can range in size from as small as a grain of sand to as large as a boulder.

Meteor

When a meteor is unfortunate enough to get pulled by gravity into a planet's atmosphere, such as Earth's atmosphere, it burns up and leaves a trail of spectacular light and color. The trial that it leaves is actually a meteor. When someone says, "Hey, look, a shooting star" or "a falling star," what they're actually referring to is a meteor.

Meteorite

If any part of meteoroid that entered an atmosphere and created a meteor makes it to the ground, it is called a meteorite. Since most meteoroids burn up completely before hitting the ground after going through Earth's atmosphere, the only meteorites we find on Earth are typically very small.

Comet

A comet is none of the above. Even though comets look like shooting stars (meteors), they most definitely are not. Comets are made of mostly ice and frozen gas. The tail of a comet, which resembles that of a meteor, is not burning; it's actually a sort of pseudo-atmosphere illuminated by the Sun's light.

Sources:

http://nineplanets.org/comets.html

http://www.enchantedlearning.com/subjects/astronomy/meteor/meteoroid.shtml

http://ssd.jpl.nasa.gov/?asteroids