Neutrino sunshine - in winter as in summer!

12 December 2001

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As the Northern Hemisphere heads towards the Winter Solstice, sunshine is in short supply at higher latitudes. But the steady flow of neutrinos from the Sun continues, by night and as well as by day, as these "ghostly" solar particles fly through the Earth as if it were not there. This image captures the Sun in "neutrino light", as recorded over a period of 500 days by the Super-Kamiokande* detector in Japan. The horizontal axis corresponds to the neutrino's "left-right" direction in the sky (right ascension), while the vertical axis corresponds to the "up-down" direction (declination). The colours are brightest where the number of neutrinos is largest. The direction of the neutrinos must be calculated from the direction of the electrons produced on the rare occasions when the neutrinos interact in the water in the detector. Scattering effects significantly smear out the actual directions, so each pixel here corresponds to about twice the Sun's actual size.

*Super-Kamiokande suffered a major accident in November 2001. This image is a reminder of some of the experiment's excellent work since the detector came into operation in 1996.

Credit: Robert Svoboda, Louisiana State University

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