Correct Option
The correct option is 1 and 3 only.
Explanation
The development of planets is generally explained through the Nebular Hypothesis and subsequent theories regarding the evolution of the solar system. Standard physical geography outline the formation of planets in three distinct stages involving the condensation of gas clouds and the accretion of matter.
Statement-wise Analysis
- Statement 1 is Correct: In the initial stage, stars begin as localized lumps of gas within a nebula. The gravitational force within these lumps leads to the formation of a gas core. Simultaneously, a huge rotating disc of gas and dust develops around this gas core.
- Statement 2 is Incorrect: In the second stage, the gas cloud condenses, and the matter around the core develops into small-rounded objects, not large gas giants. These small objects evolve through the process of cohesion into bodies known as planetesimals. Larger bodies collide and stick together due to gravitational attraction to form these planetesimals.
- Statement 3 is Correct: In the final stage, a large number of small planetesimals accrete (come together) to form fewer, larger bodies. These larger bodies are what we ultimately define as planets.
Key Takeaway: The standard sequence of planet formation involves the creation of a gas core and disc, followed by the formation of planetesimals (small-rounded objects), which finally accrete to form planets.