Sunday 10 May was the first ever SUNday. This solar observation afternoon with various additional activities was organized by the
Netherlands Institute for Space Research. Some 150 visitors (many of whom were children) came to the Infoversum, the location of the SUNdays.
Groninger Vereniging voor Weer- en Sterrenkunde
(Groningen Meteorology and Astronomy Society) and
have provided solar telescopes for these afternoons. These are equipped with special filters that make it safe to look at the sun. An ‘H-alpha filter’ lets in one specific red-coloured light, which enables you to see solar flares, huge eruptions on the sun’s surface. These flames are often several times bigger than the Earth! Visitors were amazed that solar flares can appear and disappear again in mere minutes.
Other filters block almost all sunlight (at least 99.999 percent), so that you see the sun in white with detailed dark sunspots and white filaments. At least 12 large sunspots were visible, including
Active Region 2339
(AR2339). On the Wednesday preceding the SUNday (6 May), this unleashed a gigantic solar flare that ranked in the strongest category of solar flares. The UV radiation and X-rays emitted by this eruption caused serious disruption to radio communication in the Pacific Ocean.
As well as looking through a solar telescope, the visitors also participated in various other activities. Inside, Professor of Astronomy
from the University of Groningen’s Kapteyn Astronomical Institute provided an explanation about all the things the visitors had seen on the sun.
The visitors also built their own small spectroscopes, which they could then use to split sunlight into a rainbow. In the Sunlight Game, children had to lead a particle of light through the innermost part of the sun to the outside. Many visitors combined their SUNday with a fulldome film in the Infoversum.
More SUNdays will take place on sunny Sundays until Sunday 14 June. The Blaauw Observatory will confirm two days beforehand whether the SUNday will go ahead. The series of SUNdays will end on Sunday 21 June with a special event for International SUNday. This last Sunday will go ahead regardless of the weather. For more information see
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