Asteroids
There is an area in space called the asteroid belt. This belt exists between Mars and Jupiter. Here is where millions of asteroids are found. The asteroid belt has an elliptical path, moving in the same direction as the planets.
The first asteroid was discovered in 1801; it is called Ceres. It is also the largest. Its circumference is about 960 kilometers. Like a planet, Ceres orbits around the sun. It takes 4.6 Earth years to make one orbit.
Not all asteroids are this large, however. Some are only a few hundred meters wide. Scientists think they are “junk” left over from the formation of the solar system.
Sometimes an asteroid is pulled out of its orbit. The gravitational pull of a planet or other larger object can attract it. Sometimes an asteroid crashes into a planet. This causes a crater.
We can thank Jupiter for protecting us against constant bombardment by asteroids. The Sun’s gravity pulls the asteroids toward the inner planets. But the asteroid belt is closer to Jupiter. Jupiter’s gravitational pull attracts the asteroids away from Earth. It also protects Mercury, Venus, and Mars.
Impacts are not totally impossible, however. Scientists believe that the asteroid 1950 DA will pass close to Earth. This is the greatest chance of asteroid collision for our planet. But you don’t need to worry; scientists predict it will not even come close until the year 2880!
There have been space missions to both asteroids and comets. Scientists study them to get clues about how Earth evolved. For example, some believe that the impact of an asteroid caused a chain of events that led to the extinction of the dinosaurs here on Earth. Impacts from comets may have brought water to our planet. Scientists believe that these space rocks can tell us a lot about the formation of our solar system.
(Information taken from edhelper.com and Astronomy For Kids websites)
(Photo from Daily Galaxy)
The Solar System 
i learned about the asteroid. they move around the Sun.