​The Sun is the star at the center of the Solar System. Eight planets orbit the Sun. There are 205 moons that orbit the planets of the Solar System. There are five dwarf planets in addition to the eight major planets.

​Stars and planets are regularly shaped objects: they are spheres. Many moons and some dwarf planets are also spheres. Some moons are irregularly shaped objects: they might be shaped more like potatoes than spheres.

​Asteroids are irregularly shaped rocky and metallic objects in the Solar System. Many of them orbit the Sun in a region called the asteroid belt. The asteroid belt is located between Mars and Jupiter. Asteroids can also orbit the Sun outside of the asteroid belt. Occasionally an asteroid will travel close to the Earth. It was an asteroid like this that struck the Earth 65 million years ago and caused the extinction of the large dinosaurs.

​Comets are objects made of frozen gas and dust. Comets orbit the Sun far our beyond the planets. Some comets have orbits that bring them close to the Sun. As they come close to the Sun, the heat energy of the Sun begins to melt the frozen gases in the comet. These gases begin to stream out and form a tail. The tail of the comet reflects the light of the Sun.

​

Comets can leave behind a trail of debris. These dust and sand sized particles sometimes enter the Earth’s atmosphere, burning up high above the ground. These meteors are often seen as meteor showers. Smaller asteroids sometimes enter the Earth’s atmosphere. These smaller objects often break apart, forming a fireball as they burn up. Sometimes pieces of these meteors fall all the way to the ground, and can be found as meteorites.