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No. 48: Nov-Dec 1986

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An 11-minute binary

4U1820-30 is an X-ray binary star located in the heart of the globular cluster NGC 6624. Its claim to fame is a very short period of rotation -- only 685 seconds. In just a shade over 11 minutes, a neutron star orbits a white dwarf, according to present thinking. The orbit diameter is only 1/7 the radius of our sun, which implies the stars themselves are also small. 4U1820-30 is the shortest-period binary ever found -- so short that astronomers are looking for other explanations.

Another curious fact mentioned in this item is that X-ray binaries are much more common in globular clusters than elsewhere in the universe. What is so different about globular clusters?

(King, A.R., and Watson, M.G.; "The Shortest Period Binary Star," Nature, 323:105, 1986.)

From Science Frontiers #48, NOV-DEC 1986. 1986-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:

Quotes

  • "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