Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. The discovery is particularly surprising because there was little previous indication that comets emit any significant X-radiation. 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 .
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