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Science 12 September 1997:
Vol. 277. no. 5332, pp. 1625 - 1630
DOI: 10.1126/science.277.5332.1625
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Articles

X-ray Emissions from Comets Detected in the Röntgen X-ray Satellite All-Sky Survey

Konrad Dennerl, * Jakob Englhauser, Joachim Trümper

After the unexpected discovery of x-rays emitted from comet C/1996 B2 (Hyakutake) with the Röntgen X-ray Satellite (ROSAT) in March 1996, x-ray emissions from comets C/1990 K1 (Levy), C/1990 N1 (Tsuchiya-Kiuchi), 45P (Honda-Mrkos-Pajdusáková), and C/1991 A2 (Arai), optically 300 to 30,000 times fainter than Hyakutake, were discovered in archival ROSAT data. These findings establish comets as a class of x-ray sources and allow their properties to be studied over a wide optical brightness range. The results indicate that charge exchange between highly charged heavy ions in the solar wind and cometary neutrals is the dominant process for the x-ray emission. Comets may thus be used as probes for monitoring the heavy-ion content of the solar wind.

The authors are at the Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrabeta e, D-85748 Garching, Germany.
*   To whom correspondence should be addressed. E-mail: kod{at}mpe-garching.mpg.de

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