The Sol system, also called the Solar system, the Terran system, or the Earth system, is the home star system of the human species. The system's G-class star is named Sol, hence the system's name. Sol is an average sized star in its main sequence phase, and is the dominant source of light for Earth and the other planets in the system. The Sol system is located in the Alpha Quadrant and contains 8 planets and 5 dwarf planets, for a total of 13, including the four inner terrestrial planets and the four gas giants, separated by the asteroid belt. Many smaller planetoids also orbit Sol, and many of the system's planets possess moons of varying size and number, such as Earth's satellite, Luna. In the 32nd century, the Sol system lies at the heart of the United Federation of Planets, and is one of the Federation's four core systems. The system also harbors the Charon mass relay.
The Sol system formed around 4,600,000,000 BCE. Before it began, the area of space it would eventually occupy was shielded in a dark and cold cloud of gas and dust. This dust cloud was created out of the remnants of a previous nearby supernova. Gravity urged the material to coalesce and condense, causing the cloud to spin faster and then flatten. As more and more hydrogen and helium gas were drawn to the nebula's middle, a bulge known as a protostar formed. This protostar would eventually become the star Sol.
Eventually the surrounding disk started to cool, and ever larger lumps of dust began to form into planetesimals. Over millions of years, these growing bodies continued to collide and consolidate to form the system's planets, all of which travel along their own slightly elliptical pathways, or orbits, counterclockwise around Sol. The eight major planets were Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
Human space exploration started close to home. Over their spacefaring history, humans successfully visited and, in some cases, permanently inhabited and colonized nearly all of the celestial objects in the Sol system. Venus was eventually terraformed to be more hospitable, using advanced technology to transform it despite its harsh weather and conditions. By the 32nd century, Earth's neighboring planets are well traveled enough that a shuttle service called the Jovian Run offers once-a-day travel between Jupiter and Saturn.