Earth, Moon, and Planets

, Volume 89, Issue 1–4, pp 325–343 | Cite as

Long-Period Comets and the Oort Cloud

  • Julio A. Fernández


Long-period (LP) comets, Halley-type (HT) comets, and even some comets of the Jupiter family, probably come from the Oort cloud, a huge reservoir of icy bodies that surrounds the solar system. Therefore, these comets become important probes to learn about the distant Oort cloud population. We review the fundamental dynamical properties of LP comets, and what is our current understanding of the dynamical mechanisms that bring these bodies from the distant Oort cloud region to the inner planetary region. Most new comets have original reciprocal semimajor axes in the range2 × 10-5 < 1/aorig < 5 × 10-5AU-1. Yet, this cannot be taken to represent the actual space distribution of Oort cloud comets, but only the region in the energy space in which external perturbers have the greatest efficiency in bringing comets to the inner planetary region. The flux of Oort cloud comets in the outer planetary region is found to be at least several tens times greater than the flux in the inner planetary region. The sharp decrease closer to the Sun is due to the powerful gravitational fields of Jupiter and Saturn that prevent most Oort cloud comets from reaching the Earth’s neighborhood (they act as a dynamical barrier). A small fraction of ∼10-2 Oort cloud comets become Halley type (orbital periods P < 200 yr), and some of them can reach short-period orbits with P < 20 yr. We analyze whether we can distinguish the latter, very ‘old” LP comets, from comets of the Jupier family coming from the Edgeworth-Kuiper belt.

Comets dynamics Oort cloud 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bailey, M. E.: 1983, Mon. Not. Roy. Astron. Soc. 204, 603-633.zbMATHADSGoogle Scholar
  2. Bailey, M. E., Chambers, J. E., and Hahn, G.: 1992, Astron. Astrophys. 257, 315-322.ADSGoogle Scholar
  3. Biermann, L.: 1978, in A. Reiz and T. Anderson (eds.), Astronomical Papers Dedicated to Bengt Stromgren, Copenhagen Observatory, p. 327.Google Scholar
  4. Delsemme, A. H.: 1978, Astron. Astrophys. 187, 913-918.ADSGoogle Scholar
  5. Duncan, M., Quinn, T., and Tremaine, S.: 1988, Astrophys. J. Lett. 328, L69-L73.CrossRefADSGoogle Scholar
  6. Dybczynski, P. A.: 2002, Astron. Astrophys., in press.Google Scholar
  7. Everhart, E.: 1976, in B. Donn, M. Mumma, W. Jackson, M. A'Hearn, and R. Harrington (eds.), The Study of Comets, IAU Coll. 25, NASA SP-393, pp. 445-464.Google Scholar
  8. Fernández, J. A.: 1980, Mon. Not. Roy. Astron. Soc. 192, 481-491.ADSGoogle Scholar
  9. Fernández, J. A.: 1981, Astron. Astrophys. 96, 26-35.ADSGoogle Scholar
  10. Fernández, J. A.: 1992, in S. Ferraz-Mello (ed.), Chaos, Resonance and Collective Dynamical Phenomena in the Solar System, IAU Symp. No. 152, pp. 239-254, Kluwer Academic Publishers, Dordrecht.Google Scholar
  11. Fernández, J. A.: 1994, in A. Milani et al. (eds.), Asteroids, Comets,Meteors 1993, Kluwer Academic Publishers, Dordrecht, pp. 223-240.Google Scholar
  12. Fernández, J. A.: 1997, Icarus 129, 106-119.CrossRefADSGoogle Scholar
  13. Fernández, J. A. and Gallardo, T.: 1994, Astron. Astrophys. 281, 911-922.ADSGoogle Scholar
  14. Fernández, J. A. and Gallardo, T.: 1999, in J. Svoreň, E.M. Pittich, and H. Rickman (eds.), Evolution and Source Regions of Asteroids and Comets, Astr. Inst. Slovak Acad. Sci., Tatranská Lomnica, pp. 327-338.Google Scholar
  15. Fernández, J. A. and Ip, W.-H.: 1991, in R. L. Newburn, M. Neugebauer, and J. Rahe (eds.), Comets in the Post-Halley Era, IAU Coll. No. 121, Kluwer Academic Publishers, Netherlands, pp. 487-535.Google Scholar
  16. Hills, J. G.: 1981, Astron. J. 86, 1730-1740.CrossRefADSGoogle Scholar
  17. Hut, P. and Tremaine, S.: 1985, Astron. J. 90, 1548-1557.CrossRefADSGoogle Scholar
  18. Kresák, L.: 1992, Astron. Astrophys. 259, 682-691.ADSGoogle Scholar
  19. Marsden, B. G. and Williams, G. V.: 1999, ‘Catalogue of Cometary Orbits’, 13th edn., Minor Planet Center, IAU.Google Scholar
  20. Oort, J. H.: 1950, Bull. Astron. Inst. Neth. 11, 91-110.ADSGoogle Scholar
  21. Öpik, E. J.: 1932, Proc. Am. Acad. Arts Sci. 67, 1659-1683.Google Scholar
  22. Torbett, M. V.: 1986, Mon. Not. Roy. Astron. Soc. 223, 885-895.ADSGoogle Scholar
  23. Weissman, P. R.: 1985, in A. Carusi and G. B. Valsecchi (eds.), Dynamics of Comets: Their Origin and Evolution, Reidel, Dordrecht, pp. 87-96.Google Scholar
  24. Yabushita, S. and Tsujii, T.: 1991, Mon. Not. Roy. Astron. Soc. 252, 151-155.ADSGoogle Scholar

Copyright information

© Kluwer Academic Publishers 2000

Authors and Affiliations

  • Julio A. Fernández
    • 1
  1. 1.Departamento de AstronomiaFacultad de CienciasMontevideoUruguay

Personalised recommendations