Sun: Sunspots
Sunspots are planet-sized concentrations of magnetic flux on the surface of the sun; they are sources of solar flares, coronal mass ejections and intense UV radiation.
They are cooler (and thus darker) regions on the sun where the magnetic field loops up out of the solar surface. Sunspots generally occur in pairs of opposite polarity.
Essentially, a magnetic storm on the the Sun's surface which appears as a dark area. A sunspot is approximately 1,500 to 2,500 degrees Kelvin cooler than the surrounding photosphere. The number of sunspots we see on the Sun at any given time appears to cycle every 11 years.
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Sunspots: 17th Century
Introduction - Early 1600's Using telescopes similar to Galileo Galilei’s instrument, Johannes Fabricius and Christoph Scheiner began the first systematic study of sunspots in early 1611. Johannes...
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How Low Can It Go? Sun Plunges into the Quietest Solar Minimum in a Century
April 1, 2009: The sunspot cycle is behaving a little like the stock market. Just when you think it has hit bottom, it goes even lower. 2008 was a bear. There were no sunspots observed on 266 of the...
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Oldest Written Records The two oldest written records of a sunspot observation are found in the Book of Change...
Introduction In the mid-1800s astronomers discovered from hundreds of sunspot sightings that, when they tabula...
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