Planetesimal

Definition

A planetesimal is a small celestial body that forms during the early stages of planet formation in a protoplanetary disk. They are the building blocks of planets, created through the process of accretion and collision.

5 Must Know Facts For Your Next Test

1. Planetesimals are formed from dust and gas particles clumping together in a protoplanetary disk.
2. They can range in size from a few meters to hundreds of kilometers.
3. Through repeated collisions and mergers, planetesimals can grow to form protoplanets.
4. Some planetesimals in the early Solar System became the asteroids and comets we observe today.
5. The gravitational interactions between planetesimals influence their growth and orbital dynamics.

Review Questions

• What role do planetesimals play in the formation of planets?
• How do planetesimals grow over time within a protoplanetary disk?
• What evidence do we have that some asteroids and comets were once planetesimals?

Related terms

Protoplanetary Disk: A rotating circumstellar disk of dense gas and dust surrounding a newly formed star, where planets form.

Accretion: The process by which particles stick together to form larger bodies, such as planetesimals or planets.

Protoplanet: A developing planetary body that grows by the accumulation of material through collisions with planetesimals.