Briefly outline the steps in the formation of our solar system, according to the nebular theory.
The correct answer and explanation is :
Steps in the Formation of the Solar System (Nebular Theory)
- Solar Nebula Formation – A massive cloud of gas and dust (solar nebula) begins to collapse due to gravity, possibly triggered by a nearby supernova explosion.
- Protostar Formation – As the nebula contracts, it forms a rotating disk with most of the material accumulating at the center, creating a protostar (early Sun).
- Accretion Disk and Planetary Formation – The remaining material in the disk begins to stick together, forming planetesimals (small rocky or icy bodies).
- Protoplanets Develop – Through collisions and accretion, planetesimals grow into protoplanets, which eventually evolve into planets.
- Clearing of Debris – The Sun’s strong solar wind clears out leftover gas and dust, leaving a well-defined solar system.
Explanation (300 Words)
The nebular theory is the widely accepted model explaining the formation of our solar system. Around 4.6 billion years ago, a giant cloud of gas and dust—known as the solar nebula—began to collapse under gravity. This collapse was likely triggered by an external force, such as the shockwave from a nearby supernova.
As the cloud collapsed, it started spinning due to conservation of angular momentum, flattening into a rotating disk with the young protostar (early Sun) forming at the center. The increase in pressure and temperature in the core eventually ignited nuclear fusion, officially making the Sun a star.
Surrounding the Sun, the leftover dust and gas began sticking together through a process called accretion, forming planetesimals. These small rocky and icy bodies continued to collide and merge, growing into protoplanets. Over millions of years, these protoplanets evolved into the planets we see today.
Closer to the Sun, where temperatures were high, only rocky materials could survive, leading to the formation of terrestrial planets (Mercury, Venus, Earth, and Mars). Farther away, in cooler regions, gas and ice remained intact, forming the gas giants (Jupiter and Saturn) and ice giants (Uranus and Neptune).
Once the planets had mostly formed, the young Sun emitted a strong solar wind, which blew away the remaining gas and dust, leaving behind a structured solar system. This process resulted in the formation of the planets, moons, asteroids, and other celestial bodies, shaping the solar system as we know it today.