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No. 106: Jul-Aug 1996

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The tale began on March 27, when Comet Hyakutake passed within 15 million kilometers of earth. At this point in its trajectory, it came into the field of view of the X-ray astronomy satellite ROSAT. ROSAT was designed to look at stars whose extremely high temperatures can generate X-rays. It seemed ridiculous to point ROSAT's instruments at a comet composed mainly of ice and dust. How could a comet emit X-rays? When a German-American team of scientists proposed taking a peek at Hyakutake with ROSAT, scientific eyebrowns were raised. What a waste of observing time!

At the most, the team thought they might pick up a smudge of weak X-rays where dust grains flying off Hyakutake collided with dust grains normally present in interplanetary space. The team did get ROSAT to take a look, and what the satellite saw ignited a controversy.

Some 50,000 kilometers in front of the comet was a bright crescent of X-rays, 100 times brighter than the brightest "smudge" the team of scientists had hoped for. This was completely unexpected. All astronomers could do was come up with three rather unconvincing theories: (1) Solar X-rays were absorbed and reemited by the comet (Xray fluorescence); (2) Cometary material emitted X-rays when bathed in the solar wind; and (3) Charged particles were somehow accelerated by a magnetic field compressed by the comet's bow wave in the solar wind. Nobody is particularly happy with any of these theories.

(Hecht, Jeff; "Comet Bids Farewell with Blaze of X-rays," New Scientist, p. 18, April 20, 1996. Glanz, James; "Comet Hyakutake Blazes in X-rays," Science, 272:194, 1996)

Comment. Serendipity has struck again! Imagine all the phenomena we are missing because we know they can't happen!

From Science Frontiers #106, JUL-AUG 1996. 1996-2000 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