Our solar system formed about 4.6 billion years ago from a giant cloud of gas and dust known as the solar nebula. This cloud, composed mainly of hydrogen, dust, and other gases, became gravitationally unstable and began to collapse, likely triggered by a shock wave from a nearby supernova explosion
. As the nebula collapsed, gravity pulled most of the material toward the center, where it became hot and dense enough to ignite nuclear fusion, forming the Sun. The remaining material flattened into a rotating protoplanetary disk around the newborn Sun
. Within this disk, temperatures varied: near the Sun, it was very hot, so metals and rocky minerals condensed, forming the terrestrial planets (Mercury, Venus, Earth, and Mars). Farther from the Sun, cooler temperatures allowed ices like water and ammonia to solidify, leading to the formation of the gas giants and icy bodies in the outer solar system
. Tiny dust grains in the disk collided and stuck together, gradually growing into larger clumps called planetesimals. These planetesimals continued to collide and merge over millions of years, forming protoplanets and eventually the planets we know today
. Some large collisions, such as the one that created Earth's Moon, played a significant role in shaping the planets
. After the Sun fully ignited, its solar wind cleared away much of the remaining gas and dust, leaving behind asteroids, comets, and the planets in their nearly circular orbits
. In summary, the solar system formed through the gravitational collapse of a gas and dust cloud, the birth of the Sun at its center, and the gradual coalescence of material in the surrounding disk into planets and other bodies over millions of years
