The solar nebula theory explains that the sun and planets formed about 4.6 billion years ago from a massive, rotating cloud of gas and dust called a solar nebula. As gravity caused the cloud to collapse, it spun faster and flattened into a disk, concentrating most of its mass at the center to create the sun.
- Gravitational Collapse: A giant cloud of mostly hydrogen (71%) and helium (27%), along with heavier elements, began to collapse, possibly triggered by a nearby supernova shockwave
- Flattening into a Disk: As the cloud shrank and pulled inward under its own gravity, conservation of angular momentum caused it to spin faster and flatten into a rotating protoplanetary disk
- Birth of the Sun: Over 99.8% of the material gathered at the dense center, heating up until hydrogen nuclear fission ignited to form the Sun
- Accretion of Planetesimals: In the surrounding disk, dust and ice grains acted as condensation nuclei, colliding and sticking together (accretion) to form larger bodies called planetesimal, which eventually grew into protoplanets and planets
- Terrestrial (Inner) Planets: High temperatures close to the young Sun vaporized lighter ices and gases, leaving behind rocks and metals that formed Mercury, Venus, Earth, and Mars
- Jovian (Outer) Planets: Farther away, where temperatures were much colder, water ice, ammonia, methane, and gases condensed to form the gas giants (Jupiter and Saturn) and ice giants (Uranus and Neptune) ,The Roman God's.
- Debris Fields: Leftover material formed the asteroid belt (kept from coalescing into a planet largely by Jupiter's gravity, the Kuiper belt, and the Oort cloud
- Originators: The idea was first suggested in 1755 by Immanuel Kant and later expanded in 1796 by Pierre Simon Laplace
- Evidence: Radiometric dating of meteorites, Moon rocks, and earth samples place their age consistently around 4.56 to 4.6 billion years. Modern telescope also directly observe similar circumstellar disks and star-forming nebulae across the galaxy
- Extrasolar Observations: Modern telescopes frequently image young star surrounded by real-world protoplanetary disks across the galaxy
- Flat Orbital Plane: All planets orbit the sun in roughly the same flat disk-like plane and direction.
Sun: The center of our solar system.