Letter | Published:

Gravitationally unbound comets move in predominantly retrograde orbits

Naturevolume 352pages506508 (1991) | Download Citation

Subjects

Abstract

COMETS are presumed to enter the inner Solar System from the Oort cloud, a repository of comets more than 104 AU from the Sun. Provided the perturbing effects of planetary encounters are taken into account, the original orbital energy of a comet can be calculated, and is negative or positive according to whether the comet's orbit is bound or unbound. The Oort effect1 is the tendency for the original energies of long-period (>200-yr) comets to fall within a narrow range: about 25% of such comets have original energies in the upper 0.2% of the total energy range. In addition, 10% of long-period comets are unbound, and it has been found2 that positive original energy correlates with distance of closest approach to the Sun. We report here a further correlation: unbound comets are more likely to move in retrograde orbits. We suggest that this anomaly comes about because of the omission from the orbital energy determination of non-gravitational effects arising from enhanced volatility.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1

    Oort, J. H. Bull. astr. Inst. Neth. 11, 91–110 (1950).

  2. 2

    Marsden, B. G., Sekanina, Z. & Everhart, E. Astr. J. 83, 64–71 (1978).

  3. 3

    Marsden, B. G. & Sekanina, Z. Astr. J. 78, 1118–1124 (1973).

  4. 4

    Duncan, M., Quinn, T. & Tremaine, S. Astr. J. 94, 1330–1338 (1987).

  5. 5

    Hills, J. G. Astr. J. 86, 1730–1740 (1981).

  6. 6

    Byl, J. Earth Moon Planets 36, 263–273 (1986).

  7. 7

    Heisler, J. & Tremaine, S. Icarus 65, 13–26 (1986).

  8. 8

    Heisler, J., Tremaine, S. & Alcock, C. Icarus 70, 269–288 (1987).

  9. 9

    Matese, J. J. & Whitman, P. G. Icarus 82, 389–401 (1989).

  10. 10

    Morris, D. E. & Muller, R. A. Icarus 65, 1–12 (1986).

  11. 11

    Torbett, M. V. Mon. Not. R. astr. Soc. 223, 885–895 (1986).

  12. 12

    Yabushita, S. Mon. Not. R. astr. Soc. 231, 723–733 (1988).

  13. 13

    Yabushita, S. Astr. J. 97, 262–264 (1989).

  14. 14

    Marsden, B. G. Catalogue of Cometary Orbits 6th edn (Smithsonian Astrophysical Observatory, Cambridge, Massachusetts, 1989).

  15. 15

    Meyer, S. L. Data Analysis, 254–290 (Wiley, New York, 1975).

  16. 16

    Press, W. H., Flannery, B. P., Teukolsky, S. A. & Vetterling, W. T. Numerical Recipes, 464–497 (Cambridge University Press, 1986).

  17. 17

    Leinert, C. I., Richter, I., Pitz, E. & Planck, B. Astr. Astrophys. 103, 177–188 (1981).

  18. 18

    Leinert, C. I., Roser, S. & Buitriago, J. Astr. Astrophys. 118, 345–357 (1983).

  19. 19

    Grun, E., Zook, H. A., Fechtig, H. & Giese, R. H. Icarus 62, 244–272 (1985).

  20. 20

    Marsden, B. G. & Sekanina, Z. Astr. J. 76, 1135–1151 (1971).

Download references

Author information

Affiliations

  1. Department of Physics, The University of Southwestern Louisiana, Lafayette, Louisiana, 70504-4210, USA

    • John J. Matese
    • , Patrick G. Whitman
    •  & Daniel P. Whitmire

Authors

  1. Search for John J. Matese in:

  2. Search for Patrick G. Whitman in:

  3. Search for Daniel P. Whitmire in:

About this article

Publication history

Received

Accepted

Issue Date

DOI

https://doi.org/10.1038/352506a0

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.