A color composite image of the inner coma of Comet Hyakutake made from two images using the Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2): one with a red-filter showing the dust coma and a second with an ultraviolet "Woods" filter image showing the distribution of scattered ultraviolet radiation by hydrogen atoms in the inner coma.
Credit: C. Lisse, M. Mumma (NASA/GSFC), K. Dennerl, J. Schmidt, and J. Englhauser (MPE) Explanation: The first X-rays ever detected from a comet were discovered from Comet Hyakutake with the ROSAT satellite on March 27th. The discovery is particularly surprising because there was little previous indication that comets emit any significant X-radiation. As the comet passed the Earth in late March, repeated observations with ROSAT also showed that the X-ray brightness changed over just a few hours. The crescent shape of the X-ray emission is also enigmatic. One possible explanation is that X-rays emitted from the Sun are absorbed by water in the comet's coma causing fluorescence. Another possible explanation involves interaction with the solar wind - fast moving particles streaming away from the Sun. Note, the very sharp edges in the photo are caused by the imager and do not reflect any sharp edges in the comet!
For over 1000 more images, visit the JPL Hyakutake Archive
Copyright 1997 Dr. Sten Odenwald
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