Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2012 January 21
See Explanation.  Clicking on the picture will download
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Days in the Sun
Image Credit & Copyright: Regina Valkenborgh

Explanation: From solstice to solstice, this six month long exposure compresses time from the 21st of June till the 21st of December, 2011, into a single point of view. Dubbed a solargraph, the unconventional picture was recorded with a pinhole camera made from a drink can lined with a piece of photographic paper. Fixed to a single spot for the entire exposure, the simple camera continuously records the Sun's path each day as a glowing trail burned into the photosensitive paper. In this case, the spot was chosen to look out over the domes and radio telescope of the University of Hertfordshire's Bayfordbury Observatory. Dark gaps in the daily arcs are caused by cloud cover, whereas continuous bright tracks record glorious spells of sunny weather. Of course, in June, the Sun trails begin higher at the northern hemisphere's summer solstice. The trails sink lower in the sky as December's winter solstice approaches. Last year's autumn was one of the balmiest on record in the UK, as the many bright arcs in the lower part of this picture testify.

Tomorrow's picture: saturn's hexagon

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