Formation of the Solar System

Overview

• Our solar system formed approximately 4.5 billion years ago.
• Composed of asteroids, comets, planets, and their moons.

Initial Collapse of Hydrogen Gas

• A cloud of mostly hydrogen gas and dust began to collapse onto itself.
• As it collapsed, it spun faster and flattened into a disk with a dense center.
• The center heated up, leading to the birth of the Sun.

Formation of the Sun and Planets

• Around the young Sun, a spinning disk of gas and dust existed.
• The disk cooled over time, allowing materials to coalesce due to:
  • Dew
  • Magnetism
  • Gravity
• Metals and rocks formed closer to the Sun; gases remained further away due to heat.

Formation of Planetesimals

• Cooler regions formed ices (like water) that combined to create larger bodies called planetesimals.
• These planetesimals eventually coalesced into larger planets.
• Gas giants (Jupiter and Saturn) formed as they captured surrounding gases.

Jupiter and Saturn's Formation

• Some scientists propose Jupiter formed first, drawn towards the center by swirling material in the inner disk.
• As Saturn formed, it moved inward, and both planets captured gas between them.
• They later journeyed outward together.

Asteroid Belt and Mars

• Jupiter's mass prevented rocky materials from forming larger bodies, leading to the asteroid belt.
• Jupiter's inward movement consumed much material, resulting in Mars being smaller than expected.

Early Planetary Orbits

• Within 100 million years, early planets began orbiting the Sun with leftover material in between.
• The young Sun went through a phase of strong solar winds, expelling extra material and halting growth of rocky planets and early gas giants.

Formation of Ice Giants and Oort Cloud

• Gaps caused by moving planets collected around snowball cores, leading to the formation of ice giants (Uranus and Neptune).
• Many leftover icy bodies were ejected into the Oort cloud.

Role of Comets and Collisions

• Comets brought ices and gases back to rocky planets, providing materials for atmospheres and bringing water to Earth.
• The first billion years saw many collisions from stray pieces of rock and ice.
• The Moon may have formed from a large impact with Earth; similar impacts affected the spins of Venus and Uranus.

Current Research

• Scientists are studying distant stars with exoplanets to understand planetary formation and uniqueness of our solar system.