Is a comet a giant dirty snowball?

Have you ever made a snowball on a cold day? Remember how icy it felt in your hands. Now picture a snowball with a little mud and a few tiny pebbles squished inside.

Far out in space, comets fly around the Sun with long, shining tails. People call a comet a giant dirty snowball. So is a comet really a giant dirty snowball?

Let's peek inside the very middle of a comet. That middle part is the core, which means the solid lump at the center. The core holds lots and lots of ice.

The ice holds dust and bits of rock, all frozen together. So this ice is not clean and white. It looks dark and dirty, just like a muddy snowball.

And this dirty snowball is giant! A comet's core is as big as a mountain. You could never pick it up or throw it.

Far from the Sun, space is freezing cold. Out there, the comet's core stays frozen, dark and quiet. What do you think happens when the comet flies close to the warm Sun?

The Sun warms the core, and some of its ice turns into a misty cloud. The mist carries dust out with it, like a puff from a dusty rug.

Then the Sun pushes the mist and dust far away from the comet. They stretch out into a long, shining tail. That bright tail comes from the snowball's own ice and dust!

Let's remember our special word: core. Yes, a comet's core is a giant snowball of ice mixed with dust and rock.

Next time you pat a snowball together, you can smile and think of a comet sailing through space.