Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Formation of Planetesimals: The Building Blocks of Planets

  • Anders JohansenEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_5251-1


Planetesimals are traditionally defined as solid objects (rocky or icy or a combination of both) whose internal strength is dominated by self-gravity rather than material strength. This corresponds to bodies of approximately 100 m to 1 km in size (Benz 2000). However, this definition does not take into account the role of the body in the planet-building process. Planetesimals of km in size are vulnerable to erosion and fragmentation in collisions with other planetesimals at the speeds relevant in protoplanetary disks (Ida et al. 2008). One can instead define the planetesimal formation stage as the growth of bodies to sufficient sizes to be insensitive to disruption in collisions with equal-sized bodies. This stage of planet formation may extend to as large as 1,000 km in size, depending on the strength of the gas turbulence which is responsible for inducing high planetesimal-planetesimal speeds.


Planet formation takes place in protoplanetary disks of gas and dust...


Dust Particle concentration Pebbles Planet formation Planetesimals Protoplanetary disks Streaming instability Turbulence 
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References and Further Reading

  1. Balbus SA, Hawley JF (1991) A powerful local shear instability in weakly magnetized disks. I – linear analysis. II – nonlinear evolution. Astrophys J 376:214–233CrossRefADSGoogle Scholar
  2. Barge P, Sommeria J (1995) Did planet formation begin inside persistent gaseous vortices? Astron Astrophys 295:L1–L4ADSGoogle Scholar
  3. Benz W (2000) Low velocity collisions and the growth of planetesimals. Space Sci Rev 92:279–294CrossRefADSGoogle Scholar
  4. Brauer F, Henning T, Dullemond CP (2008) Planetesimal formation near the snow line in MRI-driven turbulent protoplanetary disks. Astron Astrophys 487:L1–L4CrossRefADSGoogle Scholar
  5. Güttler C, Blum J, Zsom A, Ormel CW, Dullemond CP (2010) The outcome of protoplanetary dust growth: pebbles, boulders, or planetesimals? I. Mapping the zoo of laboratory collision experiments. Astron Astrophys 513:A56CrossRefGoogle Scholar
  6. Ida S, Guillot T, Morbidelli A (2008) Accretion and destruction of planetesimals in turbulent disks. Astrophys J 686:1292–1301CrossRefADSGoogle Scholar
  7. Johansen A, Oishi JS, Mac Low M-M, Klahr H, Henning T, Youdin A (2007) Rapid planetesimal formation in turbulent circumstellar disks. Nature 448:1022–1025CrossRefADSGoogle Scholar
  8. Johansen A, Youdin A, Klahr H (2009) Zonal flows and long-lived axisymmetric pressure bumps in magnetorotational turbulence. Astrophys J 697:1269–1289CrossRefADSGoogle Scholar
  9. Johansen A, Youdin AN, Lithwick Y (2012) Adding particle collisions to the formation of asteroids and Kuiper belt objects via streaming instabilities. Astron Astrophys 537:A125CrossRefADSGoogle Scholar
  10. Kouchi A et al (2002) Rapid growth of asteroids owing to very sticky interstellar organic grains. Astrophys J 566:L121–L124CrossRefADSGoogle Scholar
  11. Lambrechts M, Johansen A (2012) Rapid growth of gas-giant cores by pebble accretion. Astron Astrophys 544:A32CrossRefADSGoogle Scholar
  12. Levison HF, Thommes E, Duncan MJ (2010) Modeling the formation of giant planet cores. I. Evaluating key processes. Astron J 139:1297–1314CrossRefADSGoogle Scholar
  13. Lyra W, Johansen A, Klahr H, Piskunov N (2008) Embryos grown in the dead zone. Assembling the first protoplanetary cores in low mass self-gravitating circumstellar disks of gas and solids. Astron Astrophys 491:L41–L44CrossRefADSGoogle Scholar
  14. Nesvorny D, Youdin AN, Richardson DC (2010) Formation of Kuiper belt binaries by gravitational collapse. Astron J 140:785–793CrossRefADSGoogle Scholar
  15. Okuzumi S (2009) Electric charging of dust aggregates and its effect on dust coagulation in protoplanetary disks. Astron J 698:1122–1135CrossRefADSGoogle Scholar
  16. Ormel CW, Cuzzi JN, Tielens AGGM (2008) Co-accretion of chondrules and dust in the solar nebula. Astron J 679:1588–1610CrossRefADSGoogle Scholar
  17. Weidenschilling SJ (1977) Aerodynamics of solid bodies in the solar nebula. Mon Not R Astron Soc 180:57–70CrossRefADSGoogle Scholar
  18. Wurm G, Paraskov G, Krauss O (2005) Growth of planetesimals by impacts at 25 m/s. Icarus 178:253–263CrossRefADSGoogle Scholar
  19. Youdin AN, Goodman J (2005) Streaming instabilities in protoplanetary disks. Astrophys J 620:459–469CrossRefADSGoogle Scholar
  20. Zsom A, Ormel CW, Güttler C, Blum J, Dullemond CP (2010) The outcome of protoplanetary dust growth: pebbles, boulders, or planetesimals? II. Introducing the bouncing barrier. Astron Astrophys 513:A57CrossRefADSGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Lund UniversityLundSweden