Which statement accurately describes planetesimals? They are the origins of planets. They formed from ice and rocks. They were created during the big bang. They contain 98% of matter in the solar system.
The Correct Answer and Explanation is :
The correct statement is: “They are the origins of planets.”
Explanation:
Planetesimals are small, solid objects that formed from dust, gas, and other materials in the early solar system. They are considered the building blocks of planets and other larger bodies, such as moons and asteroids.
Formation:
Planetesimals formed about 4.6 billion years ago during the early stages of the solar system’s formation. They originated from the protoplanetary disk—a rotating disk of gas and dust that surrounded the young Sun. As the dust particles in this disk collided and stuck together due to electrostatic forces, they formed larger and larger clumps. Over time, these clumps continued to collide and merge, eventually becoming planetesimals, which are typically a few kilometers in diameter but could range much larger.
Role in Planet Formation:
Planetesimals played a crucial role in the formation of planets. As they continued to collide and accumulate more material, some grew large enough to become proto-planets. Through further collisions, these proto-planets eventually coalesced into the planets we see today. This process of accretion, where smaller bodies stick together to form larger ones, is fundamental to the growth of planets.
Other Options:
- “They formed from ice and rocks”: While some planetesimals did contain ice and rock, this description is too narrow. Planetesimals could be composed of various materials depending on their location in the solar system, including metals, silicates, and volatiles.
- “They were created during the Big Bang”: This is incorrect. The Big Bang occurred about 13.8 billion years ago, long before the formation of the solar system. Planetesimals formed much later as part of the process of star and planet formation.
- “They contain 98% of matter in the solar system”: This is inaccurate. The Sun contains about 99.86% of the solar system’s mass. Planetesimals, while significant in the early solar system, are much smaller in comparison.
Thus, the statement that planetesimals “are the origins of planets” is the most accurate.