Solar system

The Solar System is a stellar formation within the Orion Arm of the Milky Way Galaxy, formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with the majority of the remaining mass contained in Jupiter. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being primarily composed of rock and metal. The four outer planets are giant planets, being substantially more massive than the terrestrials. The two largest planets, Jupiter and Saturn, are gas giants, being composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are ice giants, being composed mostly of substances with relatively high melting points compared with hydrogen and helium, called volatiles, such as water, ammonia and methane. All eight planets have almost circular orbits.

Space Exploration
Man first began exploring the Solar System using rudimentary tools, and subsequently found ways to engage in physical exploration, with space vessels. The first such was the Vostok vessel.

The 21st Century saw an increased exploration and exploitation of the Solar System's asteroids, with the first settlements in space being space stations.

In the 22nd Century, the vessels used for space exploration featured artificial gravity for the first time.