Formation of the Solar System

Scientific Theories on Formation of the Solar System

Nebular Hypothesis (Modern Nebular Theory)

• Massive molecular cloud collapsed under gravity to form the solar system around 4.6 billion years ago
• Sun originated at the center of the collapsing mass, with the remaining mass flattening into a protoplanetary disc
• Planets, moons, and other objects formed from this disc through accretion
• Angular momentum played a crucial role in forming the disc
• Disc temperature variations impacted planet makeup
• The "frost line" divides the development of rocky and gaseous planets

Theories on Formation of the Planets

• Modern Nebular Theory: solar nebula collapsed to form the Sun and planets
• Rocky materials formed terrestrial planets (Mercury, Venus, Earth, and Mars) near the Sun
• Gas giants (Jupiter and Saturn) formed further away from the Sun
• Alternative theories: encounter hypothesis, protoplanet hypothesis, and migration idea

Theory on Formation of the Moons (Giant Impact Hypothesis)

• Oblique collision between proto-Earth and Theia (a planetary body the size of Mars) around 4.5 billion years ago
• Impact launched debris into orbit, which gradually formed the Moon over weeks to years
• Moon's composition is iron-depleted, similar to Earth's mantle
• Supporting evidence: identical oxygen isotope ratios in rocks from Earth and Moon

Theory on Formation of Asteroids (Asteroid Belt Formation Theory)

• Asteroid belt was initially empty and formed from excess rocky material during the formation of terrestrial planets
• Material was gravitationally flung outward, implanting S-type (stony) asteroids into the inner main belt
• Gas giants' formation destabilized neighboring planetesimals, injecting C-type (carbon-rich) asteroids into the outer main belt

Theories on the Formation of Comets

• Comets likely formed in outer areas beyond the "frost line" around 4.6 billion years ago
• Comets come from the Kuiper Belt and Oort Cloud
• Comet composition: solid bodies made of ice, dust, and small rock fragments
• Comets are a mixture of water ice and other volatile substances that evaporate when approaching the Sun

Learn about the scientific theories behind the formation of the solar system, including the Nebular Hypothesis and its role in shaping our cosmic neighborhood.