The Solar System is a vast, gravitationally bound structure consisting of the Sun, eight Planets, their moons, and countless smaller bodies such as asteroids, comets, and dwarf planets, all orbiting within a complex cosmic environment.
The History of Solar System
Formation of the Solar System
4.6B years ago
◦ A giant molecular cloud of gas and dust collapses under gravity.
◦ Most of the material gathers into the Sun; the rest forms a rotating protoplanetary disk.
Birth of Planetesimals
4.56B years ago
◦ Dust particles stick together, forming kilometer-sized bodies (planetesimals).
◦ Early collisions create the building blocks of planets, moons, and asteroids.
Further Planet Formation
4.5B years ago
◦ Planetesimals collide and stick, forming protoplanets.
◦ Some collide violently, shaping planets’ surfaces.
Heavy Bombardment Period
4.4–4.0B years ago
◦ Intense asteroid and comet impacts shape planetary surfaces.
◦ Early oceans and atmospheres begin forming on Earth and possibly Mars.
First Signs of Life on Earth
3.8–3.5B years ago
◦ Microbial life emerges on Earth.
◦ Mars may have had liquid water and possibly habitable conditions.
Planetary Cooling & Evolution
3.0–2.0B years ago
◦ Volcanic activity and tectonics reshape planets.
◦ Outer planets’ moons (e.g., Europa, Enceladus) develop subsurface oceans.
Stable Era
1.0B years ago
◦ Solar System enters a relatively stable orbital arrangement.
◦ Slow, occasional asteroid/comet impacts continue.
Dinosaur Extinction Impact
65M years ago
◦ A large asteroid hits Earth near present-day Yucatán Peninsula, causing mass extinction.
Mature Solar System
Present Day
◦ Eight planets, over 200 moons, millions of asteroids, and countless comets orbit the Sun.
◦ Human spacecraft explore planets, moons, and interstellar space.
Sun’s Red Giant Phase
In 5B years
◦ Sun exhausts hydrogen fuel, expands, and engulfs inner planets (possibly Earth).
White Dwarf Sun
In 7B years
◦ Sun sheds its outer layers, leaving behind a dense white dwarf surrounded by a planetary nebula.
