Definition of planetesimal in English:

planetesimal

noun

Astronomy
  • A minute planet; a body that could or did come together with many others under gravitation to form a planet.

    • ‘Although planets, moons and planetesimals may seem to be very different astronomically, their common origin shows that this is not so.’
    • ‘Asteroids are small bodies in space - the numerous leftover planetesimals from which the planets were made nearly 4.6 billion years ago.’
    • ‘When the planets formed 4.6 billion years ago, they formed from an agglomeration of many planetesimals, or small solid celestial bodies.’
    • ‘Like the hills and valleys on a contour map the gravity wells of suns, planets, moons, and planetesimals showed up.’
    • ‘As planetesimals grow still larger, their gravitational attraction increases, allowing them to become even more effective at accreting nearby planetesimals.’

adjective

Astronomy
  • attributive Relating to planetesimal bodies.

    • ‘His greatest contribution, however, was his planetesimal hypothesis of the origin of the planets.’
    • ‘After all, planetesimal sized portions of the Solar System cannot be considered to be orbiting the Earth, except in the obvious case of the Moon.’
    • ‘Models of planetesimal disks suggest that low relative velocities between the bodies produce accretion (objects hit and stay together) rather than fragmentation (objects break up and disperse).’

Origin

Early 20th century: from planet, on the pattern of infinitesimal.

Pronunciation

planetesimal

/ˌplanəˈtesəməl/