On Earth, a rock is a rock . . . right?  Of course not!  There are boulders!  There are pebbles!  There are flat rocks that are perfect for skipping across water.  There are pet rocks!  And there are Pop Rocks!  Those are the only rocks you can eat.  The others will break your teeth.  In space, there are very different kinds of rocks.  It depends on where they are, what they are doing, and how big they are.  Warning: do not eat, skip, or pet space rocks. 

Let's begin way, way, way out in space.  A comet is a big piece of ice and rock that has a shiny tail behind it and is found on the very edge of our space neighborhood.  A comet is made of ice and gases that make a cloud around it called a coma.  You can see its tail when it passes close to a star and the ice around it starts to melt, trailing a light line of melting water.  Grab a butterfly net and stick it way up into space to try to catch one. You won't, though.

Hailey's Comet may be the most famous of the comets.

As we take some steps closer to the sun, we will start to see some bodies spinning around the sun that are a lot bigger than a comet.  A dwarf planet is a very big piece of rock that moves around a star and is big enough to be round but is not big enough to be a called a planet.  We think there are a lot of these in our space neighborhood.  We thought some of these were planets for a time but then figured out were too small.  Sorry, Pluto.  You will be missed by the planet family.  All of these can be found out past all the planets, or in the asteroid belt.  If one of these ever comes close to Earth, put away your butterfly net . . . and say bye to everyone. 

Just in case you're in the market for a dwarf planet. Here are three to choose from.

If we look in the middle of our solar system, we will find a long stretch of open space between Mars and Jupiter.  This is filled with many flying rocks of all different shapes and sizes.  An asteroid is a very big piece of rock that stays in one part of the solar system most of the time, but can also be pulled in by a planet or star.  Since they are made of rock, they do not have those pretty tails.  They are also always bumping into each other, so there are marks all over them where different things have smashed into them.  Your butterfly net will not reach those either. 

Wow, so that's what an asteroid looks like up close. Looks like the moon to me.

Last and indeed least, we have the smallest rocks floating around space.  A meteor is a rock that falls down to Earth from space and can glow super bright.  You have heard about these before.  You might have even seen one.  Shooting stars.  Wishing stars.  White lines through the sky.  If you have found a rock from space on Earth, it used to be a meteor.  These can be as big as thirty school buses, but most that make it through Earth's air will burn up as they come falling down.  Some of them will land as just small rocks.  Yes!  You can catch one of these with your butterfly net!  You will just have a hole in the end of the net. 

A meteor shower can put on quite a light show.

Just like on Earth, there are many kinds of rocks in space.  There are big pieces of rock and ice on the edge of our space neighborhood.  There are huge rocks that are too small to be planets, which move around the sun just like planets.  There are rocks that fly through the open space between Mars and Jupiter.  Last, there are rocks that you can see streaking through the night and that will sometimes land on Earth as small rocks.  You cannot catch most of these, but that should not stop you from reaching for the stars . . . with your butterfly net.


Universe Today.  "What's the Difference Between a Comet, Asteroid, and Meteor?"  Universe Today, 2013.  <http://www.universetoday.com/100075/>

Universe Today.  "Dwarf Planet"  Universe Today, 2013.  <http://www.universetoday.com/72717/what-is-a-dwarf-planet/>