- The solar system formed about 4.6 billion years ago from a giant cloud of gas and dust called a nebula.
- Gravity caused the nebula to collapse and spin, forming a rotating disk with a dense center that became the Sun.
- Dust and gas in the disk clumped together through collisions and gravity, forming planetesimals, which eventually grew into planets.
- The inner planets (Mercury, Venus, Earth, Mars) are rocky because heat near the Sun vaporized lighter materials.
- The outer planets (Jupiter, Saturn, Uranus, Neptune) are gaseous or icy because colder temperatures allowed gases and ices to condense and accumulate.
- Leftover debris became asteroids, comets, and other small bodies scattered throughout the solar system.
Parent Tip: Review the logic above to help your child master the concept of formation of the solar system worksheet.
