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No. 50: Mar-Apr 1987

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Too many short-period comets

Some comets, such as Halley's, have periods of less than 200 years. Scientists have postulated that these comets, which orbit relatively close to the sun, originally came from the far-distant Oort Cloud on parabolic (non-returning) orbits around the sun. Perturbations by the planets, notably Jupiter, deflected them into the tighter orbits we see today. The problem is that the number of parabolic comets entering the inner solar system from the Oort Cloud of comets (located at the outermost fringes of the solar system) is 100 times too small to account for the existing population of short-period comets. M.E. Bailey believes this discrepancy can be removed if the Oort Cloud possesses a massive inner core of comets.

(Bailey, M.E.; "The Near-Parabolic Flux and the Origin of Short-Period Comets," Nature, 324:350, 1986.)

Reference. The Oort Cloud of comets is an entrenched part of astronomical dogma. For observations challenging its existence, see our catalog: The Sun and Solar System Debris. A description of this book may be found here.

From Science Frontiers #50, MAR-APR 1987. 1987-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987