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How Much Do You Know About Asteroids?

© Dina Ely

Most people don't know very much about asteroids. And a lot of what people do know is fiction, not fact!

Many movies depict asteroids as dangerous space-rocks lurking just beyond our orbit, threatening to destroy entire planets in collision. In reality, asteroids are space junk, and you don't have to worry about an an asteroid hitting Earth anytime soon. Scientists guess that asteroids don't hit our planet any more frequently than once in every 100 million years! So we are safe.

Dinosaurs may not have been so lucky, though. The common theory behind their extinction is that an asteroid or comet hit the Earth 65 million years ago. The impact triggered a massive climate change (places that were hot became cold, and places that were cold became hot) and violent weather storms. But don't worry. Even if the scientists are right, and an asteroid did hit the planet back then, by their calculations there will be at least another 35 million years until another asteroid will come close enough to strike!

Asteroids are literally garbage left over from the formation of our solar system. They float through space and would become new planets if they were large enough to emit sufficient gravity. Without enough gravity, asteroids can't attract other asteroids, so they never come together in planetary form. And even if all the asteroids in the entire solar system came together, the resulting planet would still be smaller than Earth's Moon!

There is an asteroid belt (a collection of asteroids close together) in our solar system. It's divided into two sections: the inner belt and the outer belt. The inner belt is made up of asteroids that are less than 250 million miles from our Sun. The outer belt is made up of asteroids that are 250 million miles from the Sun. The vast majority of asteroids float in either the inner or outer belt. (Only a few asteroids exist outside the asteroid belt.)

There are approximately 26 large asteroids in our solar system. There are millions of others that can be so small they are the size of a single grain of sand! The largest asteroid in our solar system is called "Quaoar", and even that is only one tenth of the size of our planet! Another large asteroid which was discovered in 2001 is called "2001 KX76", which orbits near Pluto. Until the discovery of 2001 KX76 the asteroid "Ceres" was thought to be the second-biggest asteroid in our solar system. Ceres is now known to be the third-biggest.

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