planetesimals
Early solar fragments
Planetesimals are small rocky or icy bodies that formed in the early solar system from dust and gas clumping together.
Ranging from meters to kilometers across, they served as building blocks—colliding and merging over millions of years to form planets and moons.
The term appears in discussions of planetary formation: Asteroids are remnants of planetesimals that never coalesced into a planet.
Growth through external addition
- dustFine settled particles
- collisionsForceful contacts between objects
- aggregationCombined collection of items
- clumpingForming into lumps
condensation · building blocks · embryos · oligarchs · differentiation · gravity · growth · coalescence
Small solar orbiters
- cometsIcy bodies orbiting stars
- Kuiper beltDistant ring of frozen objects
- Oort cloudTheoretical cometary halo
- asteroid beltPlanetary rubble orbit zone
meteoroids · debris · Ceres · Vesta · Pluto · centaurs · near-Earth objects · Sedna
Covered with stones
- icyFrozen or unfriendly
- silicatesSilicon-oxygen bonded minerals
- ironElement twenty-six
- nickelElement twenty-eight, or coin
carbonaceous · primordial · heterogeneous · undifferentiated · refractory · organic compounds · water ice · ammonia
Planets of hydrogen, helium
- primordialExisting from the start
- solar nebulaGas cloud forming stars
- embryosEarliest developmental organisms
- protoplanetsEarly-stage planet formations
accretion
Growth through external addition
- dustFine settled particles
- collisionsForceful contacts between objects
- aggregationCombined collection of items
clumping · condensation · building blocks · embryos · oligarchs · differentiation · gravity · growth · coalescence · agglomeration
asteroids
Small solar orbiters
- cometsIcy bodies orbiting stars
- Kuiper beltDistant ring of frozen objects
- Oort cloudTheoretical cometary halo
asteroid belt · meteoroids · debris · Ceres · Vesta · Pluto · centaurs · near-Earth objects · Sedna
rocky
Covered with stones
nickel · carbonaceous · primordial · heterogeneous · undifferentiated · refractory · organic compounds · water ice · ammonia · methane
gas giants
Planets of hydrogen, helium
- primordialExisting from the start
- solar nebulaGas cloud forming stars
- embryosEarliest developmental organisms
planetesimalsplanets
Star-orbiting celestial bodies
terrestrial planets · gas giants · major planets · Earth · Jupiter
planetesimalsgiant planets
Huge low-density worlds
stars · gas giants · brown dwarfs · cosmic dust · interstellar dust