Definition of planetesimal in English:

planetesimal

noun

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

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

adjective

Astronomy
  • Denoting or relating to planetesimals:

    ‘the planetesimal material orbiting the sun’
    • ‘His greatest contribution, however, was his planetesimal hypothesis of the origin of the planets.’
    • ‘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).’
    • ‘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.’

Origin

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

Pronunciation:

planetesimal

/ˌplanɪˈtɛsɪm(ə)l/