The Nobel Prize in Physics 2002
Masatoshi Koshiba
International Centre for Elementary Particle Physics, University of Tokyo, Japan
The Supernova 1987A
The neutrinos arrived at 07:35 on
23 February 1987.
Photo: The Anglo-Australian Observatory
There is a clear increase in the
signal for neutrinos coming from the sun.

Masatoshi Koshiba followed up on the measurements made by Raymond Davis Jr by developing a large water-filled detector, called Kamiokande, in a Japanese mine. Kamiokande was direction sensitive and could confirm Davis' discovery that neutrinos came from the sun. The detector was operating on 23 February 1987 and detected 12 of the 1058 neutrinos emitted by supernova 1987A when it exploded 170,000 light years from the earth – the first clear observation of neutrinos produced outside our galaxy.

The Kamiokande water tank was lined with photomultipliers. When neutrinos enter the tank, they can interact with electrons. These produce flashes of light, which are registered by the photomultipliers.
Photo: Kamioka Observatory

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