Planetesimals and planets are both celestial bodies, but they differ significantly in terms of size, formation, and development.
Planetesimals are small, solid objects that form in the early stages of the solar system’s development. They typically range in size from a few meters to several hundred kilometers across. These bodies are considered the building blocks of planets and are formed through the process of accretion, where dust and gas in the protoplanetary disk come together under the influence of gravity.
On the other hand, planets are much larger bodies that have undergone significant growth and differentiation. They are formed from the accumulation of numerous planetesimals, alongside gas and ice, eventually becoming massive enough to clear their orbits of other debris. Planets are generally recognized as having sufficient mass to achieve hydrostatic equilibrium, giving them a rounded shape, and they have cleared their orbital zones of other objects.
In summary, the key differences are:
- Size: Planetesimals are smaller and vary from a few meters to hundreds of kilometers, whereas planets are significantly larger, typically thousands of kilometers in diameter.
- Formation: Planetesimals form from the accretion of dust and gas in the protoplanetary disk, while planets grow by accumulating more planetesimals and other materials over time.
- Orbital Clearing: Planets have cleared their orbits of other debris, while planetesimals have not yet reached that stage of development.
Understanding these differences helps astronomers and planetary scientists trace the evolution of our solar system and other planetary systems throughout the universe.