Theorys about the universe.

 Claudius Ptolemy
(AD 100-165), a great Greek astronomer, argued that the stars and planets moved around the Earth in circles, because the circle was a perfect shape created by the gods. This is what scientist call the Geocentric theory. His description of how the universe worked was accepted for more than 1,500 years, when
Nicolas Copernicus (1473-1543) noticed that the movements of the Earth could be better explained if the Sun, not the Earth, lay at the centre. This is called the Heliocentric theory. Like Ptolemy, Copernicus believed that the planets moved in circles, but Johannes Kepler (1571-1630) showed that their orbits were elliptical (oval-shaped).

Our solar system.

see more in the book space (usborne discovery)

About 10000 million years after the Big Bang, our Sun formed. Vast clouds of gas swirling around it became the planets and moons of our Solar System. Today, parts of the universe are still forming from dense clumps of gas.

The universe

The universe is so huge that no one really knows for sure exactly how big it is. It´s made up of billions of stars , planets, moons, enormous clouds of gas  and the giant empty spaces in between empty spaces in between.
*If you want to know more look in the book Space (usborne discovery)