A sunspot is a region on the Sun's surface (photosphere) that is marked by a lower temperature than its surroundings and intense magnetic activity, which inhibits convection, forming areas of low surface temperature.

Although they are blindingly bright at temperatures of roughly 4000-4500 K, the contrast with the surrounding material at some 5700 K leaves them clearly visible as dark spots.

If they were isolated from the surrounding photosphere they would be brighter than an electric arc.

Sunspot numbers have been recorded since 1700 AD and estimated back to 11,000 BP.

The recent trend is upward from 1900 to the 1960s, then somewhat downward.

The Sun was last similarly active over 8,000 years ago..

For more information about the topic Sunspot, read the full article at Wikipedia.org, or see the following related articles:

Solar flare — A solar flare is a violent explosion in the Sun's atmosphere with an energy equivalent to tens of millions of hydrogen bombs. Solar flares take place ...  > read more

Corona — In astronomy, a corona is the luminous plasma "atmosphere" of the Sun or other celestial body, extending millions of kilometres into space, most ...  > read more

Geomagnetic storm — A geomagnetic storm is a temporary disturbance of the Earth's magnetosphere. Associated with solar coronal mass ejections, coronal holes, or solar ...  > read more

Sun — The Sun is the spectral type G2V yellow star at the center of our solar system. About 5 million tons of matter is converted by the Sun's core into ...  > read more

Related Stories

Astrophysicists Solve Mystery Of Gas Flow From Sunspots (December 4, 1997) — One of the classic problems of solar physics has been solved, and the solution turns out to be a model of solar gas flow first proposed by a University of Rochester astrophysicist in ...  > read more

Powerful 'Conveyer Belts' Drive Sun's 11-year Cycle, New Evidence Suggests (June 20, 2003) — NASA and university astronomers have found evidence that the 11-year sunspot cycle is driven in part by a giant conveyor belt-like, circulating current within the ...  > read more

The Sun's Dark Secret: How Sunspots Pull Themselves Together (November 13, 2001) — Scientists now have the first clear picture of what lies beneath sunspots, enigmatic planet-sized dark areas on the Sun's surface, and have peered inside the Sun to see swirling flows of ...  > read more

Sunspot Cycle Closely Following Prediction -- Maximum Expected In The Year 2000 (October 20, 1998) — Scientists at NASA's Marshall Space Flight Center appear to have done a good job of predicting Cycle 23 of the sunspot cycle. "Except for the last few days, it's followed our curve very ...  > read more

Changes In Solar Brightness Too Weak To Explain Global Warming (September 14, 2006) — Changes in the sun's brightness over the past millennium have had only a small effect on Earth's climate, according to a new study appearing in Nature. The results imply that human activities are ...  > read more

Search ScienceDaily

Spotting Sun Spots