Astrophysics and Space Science

, Volume 31, Issue 2, pp 385–401 | Cite as

The non-existence of the Oort cometary shell

  • R. A. Lyttleton


The procedures adopted as theory for a shell of comets are shown to be invalid. Any plot of numbers of Long-period comets against 1/a will automatically exhibit a peak at small values of this parameter, and cannot be inverted to demonstrate a high volume-density of aphelia in space. The positions of actual aphelion-points show no sign of any concentration at any range. Further, the aphelion-distance undergoes large almost random changes owing to planetary perturbations at each return, and present values can yield no indication of original positions. That a group of some forty, or even twenty, comets selected for other reasons would all be coming in for the first time has such evanescent probability as to be an entirely inadmissible assumption. Moreover, if comets were perturbed from almost circular motion in the supposed shell to the observed almost parabolic motions, the requisite changes of energy would in general displace the new aphelion-points far outside the shell, so that again the latest aphelion-distances could afford no indication of the position of the shell. To maintain the supply of observable long-period comets by means of stellar perturbations from the shell would require there to be hundreds of stars currently within distance of the order of a parsec from the Sun. The suggested origin for the comets of the shell as having being ‘born’ by unspecified process at planetary distances, from there to be ejected by planetary action to the domain of the shell, and for these orbits then to be rounded up by stellar action is contrary to every consideration of dynamical theory. A recent attempt to save the shell-theory by making use solely of comets with large perihelion-distance is shown to rest on exactly the same errors as have done all the earlier presentations. The plain conclusions emerge that the shell-theory is devoid of any support by facts, and that the alleged shell of comets is non-existent.


Original Position Dynamical Theory Recent Attempt Circular Motion Early Presentation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Brady, J. L.: 1965,Astron. J. 70, 279Google Scholar
  2. Brady, J. L.: 1971,Astron. J. 76, 728.Google Scholar
  3. Everhart, E. and Raghavan, N.: 1970,Astron. J. 75, 258.Google Scholar
  4. Galibina, M.: 1963,Bull. Inst. Theor. Astron. 9, 496.Google Scholar
  5. IAU Symp 45: 1972, G. A. Chebotarev, E. I. Kazimirchak-Polonskaya, and B. G. Mardsen (eds.), ‘The Motion, Evolution of Orbits, and Origin of Comets’, D. Reidel Publ. Co., Dordrecht.Google Scholar
  6. Lyttleton, R. A.: 1972,Monthly Notices Roy. Astron. Soc. 158, 463.Google Scholar
  7. Lyttleton, R. A. and Hammersley, J. M.: 1964,Monthly Notices Roy. Astron. Soc. 127, 257.Google Scholar
  8. Marsden, B. G. and Sekanina, Z.: 1973,Astron. J. 78, 1118.Google Scholar
  9. Oort, J. H.: 1950,Bull. Astron. Inst. Neth. 11 (408), 91.Google Scholar
  10. Oort, J. H.: 1951,Observatory 71, 129.Google Scholar
  11. Oort, J. H.: 1963,The Solar System, Vol. 4, Ch. 20, Chicago, pp. 665–673.Google Scholar
  12. Porter, J. G.: 1952,Comets and Meteor-Streams, Chapman & Hall, London, p. 51.Google Scholar
  13. Strömgren, E.: 1910,Vierteljahrsschrift Astron. Gesellschaft IV.Google Scholar
  14. Strömgren, E.: 1914,Mem. Acad. Sci. Copenhagen XI, 4.Google Scholar
  15. Strömgren, E.: 1914,Copenhagen Obs. Publ. 19.Google Scholar
  16. Strömgren, E.: 1935,Copenhagen Obs. Publ. 98.Google Scholar
  17. Tyror, J. G.: 1957,Monthly Notices Roy. Astron. Soc. 117, 1.Google Scholar

Copyright information

© D. Reidel Publishing Company 1974

Authors and Affiliations

  • R. A. Lyttleton
    • 1
    • 2
  1. 1.Institute of AstronomyCambridgeEngland
  2. 2.Jet Propulsion LaboratoryPasadendUSA

Personalised recommendations