Our solar system has one star, the Sun, with eight planets and the dwarf planets orbiting around it. Moons that orbit planets are called natural satellites and are also part of the solar system. The whole solar system is a small part of the Milky Way galaxy.
The Sun formed from a cloud of dust and gas called a nebula. Gravitational attraction pulled the dust and gas together. As the material was squashed, the core became hot and dense enough for fusion reactions to start, and the star began to give out energy.
A star then stays stable for billions of years. Gravity tries to make the star collapse inwards, while the energy released by fusion makes the star expand outwards. When the two balance, the star is in equilibrium and stays the same size.
