The Solar System is made up of all the planets that orbit our Sun. In addition to planets, the Solar System also consists of moons, comets, asteroids, minor planets, and dust and gas. Scientists believe that the solar system was formed when a cloud of gas and dust in space was disturbed, maybe by the explosion of a nearby star (called a supernova). This explosion made waves in space which squeezed the cloud of gas and dust. Our solar system consists of one star (the Sun), eight planets and all their moons, three dwarf planets, and several thousand small solar system objects—asteroids, comets, trans-Neptunian objects, and other small bodies. The Sun’s age was calculated in 1989 to be 4.5 billion years old, less than the 4.7 billion years previously believed. On the other hand, it is in our exploration of the solar system that our observations and understanding have come such a long way since the Greek astronomers started us on this road of scientific exploration. So, will consider how the basic properties of the solar system relate to the formation process. As we shall discuss, there is strong evidence that the solar system formed about 4.5 billion years ago and it took about 500 million years for the planets to form in more or less their current location and orbits. In subsequent sessions we shall consider how the planets and other solar system material evolved for the next 4 billion years.