At the center of our solar system is the Sun. It is a star, like millions of other stars in the sky. Other objects in the solar system travel around the sun. The planets are the largest of all these objects. Every planet has something in common with the Earth, but also every planet has even more that is different in relation to the Earth.
The planets closest to the sun are called the inner planets. These are Mercury, Venus, Earth and Mars. After them is a large ring of asteroids, pieces of rock much smaller than the planet. This ring is called the Asteroid Belt. Behind the Asteroid Belt is a dwarf planet called Ceres. Then come the outer planets: Jupiter, Saturn, Uranus and Neptune. Still further are two dwarf planets, Pluto and Eris.
Behind Neptune's orbit is another large ring of asteroid-like objects, called the Kuiper Belt. It was named after the scientist who first wrote about it.
The Kuiper belt is followed by the Oort cloud. Scientists think that most comets that pass through the solar system come from there.
There is dust between all these things. The dust particles are very distant from each other, but they glow in sunlight. Before dawn (in September or October) we can see that reflection in the east. We call this the zodiac glow. When pieces of space dust hit the Earth's atmosphere, they burn. If they are larger pieces, their combustion is better seen from the Earth and we call it meteors.
Why do all the planets revolve around the Sun? Why do moons revolve around planets? Why doesn't the sun set sail and leave the planets alone? The answer to all these questions is related to gravity. Gravity is a force associated with mass. She keeps things together.
The sun's gravity is strong enough to keep the Earth in its "vicinity". The sun does not stand in one "place" in the universe. The entire solar system orbits the center of our galaxy (the Milky Way). All these objects are held together by gravity.
In 1543, Nicolaus Copernicus discovered that the planets revolved around the Sun, and that only the Moon revolved around the Earth. Yet all his life he was afraid to tell anyone, because at that time in Europe he could be burned at the stake for it. Nowadays, astronomers are discovering more and more. They have recently found more objects like Pluto. One of them, Eris, is even bigger than Pluto. Because of all this, Pluto is no longer an ordinary planet, but is called a "dwarf planet".