The correct option is 2 and 3 only.
Explanation
In the context of the formation of the solar system, particularly under the Planetesimal Hypothesis and the Nebular Hypothesis, planetesimals are solid objects thought to exist in protoplanetary disks and debris disks. They serve as the fundamental building blocks of planets.
Statement-wise Analysis:
- Statement 1 is Incorrect: Planetesimals are not formed by the disintegration of objects. Instead, they are formed by the cohesion and accretion of gas clouds and dust particles. Under the force of gravity and other physical forces, these small particles condense and stick together to form larger bodies known as planetesimals.
- Statement 2 is Correct: Planetesimals are significantly smaller than the final planets. They range in size from a few kilometers to hundreds of kilometers in diameter. They represent an intermediate stage in planetary growth.
- Statement 3 is Correct: The core mechanism of planetary formation involves the collision and gravitational attraction of planetesimals. Through a process called accretion, these bodies collide and merge over time to form larger bodies called protoplanets, which eventually evolve into planets.
Key Takeaway:
Planetesimals are the initial, smaller solid bodies formed by the accretion of dust and gas in a solar nebula, which subsequently merge through collision and gravity to form planets.