Summary
Highlights
Our solar system formed approximately 4.5 billion years ago from a collapsing cloud of interstellar gas and dust, creating a swirling disc of material. It is located in the Milky Way's Orion star cluster, and our sun is one of the 15% of stars in the galaxy that host planetary systems.
The eight planets are divided into two categories: Terrestrial and Jovian. Terrestrial planets (Mercury, Venus, Earth, Mars) are rocky, have solid surfaces, few or no moons, no ring systems, and are relatively small. Mercury is the closest to the sun, Venus is the hottest, Earth is the only known planet to sustain life, and Mars may have supported life in the past.
Beyond the terrestrial planets are the Jovian planets. These include gas giants Jupiter and Saturn, predominantly made of hydrogen and helium, and ice giants Uranus and Neptune, which also contain rock, ice, water, methane, and ammonia. All Jovian planets have multiple moons, ring systems, no solid surface, and are immense, with Jupiter being the largest planet in the solar system.
The asteroid belt, a disc of rocky objects and remnants, orbits between the terrestrial and Jovian planets. Further out is the icy Kuiper Belt, home to dwarf planets like Pluto and many comets. Beyond that lies the Oort Cloud, a vast, spherical collection of icy debris, marking the gravitational and physical edge of the solar system.