Solar System

• Within our solar system there is one star, the Sun, plus the eight planets and the dwarf planets that orbit around the Sun
• Natural satellites, the moons that orbit planets, are part of the solar system
• Our solar system is a small part of the Milky Way galaxy
• The Sun was formed from a cloud of dust and gas (nebula) pulled together by gravitational attraction
• Fusion reactions in stars lead to an equilibrium between the gravitational collapse of a star and the expansion of a star due to fusion energy
• When the temperature of a protostar is high enough hydrogen nuclei fuse together to form helium