Ian
priscilla 1Sunspot
May 29th 2009 07:30
A sunspot is a region on the Sun's surface that is marked by intense magnetic activity, which inhibits convection, forming areas of reduced surface temperature. They can be visible from Earth without the aid of a telescope. Although they are at temperatures of roughly 4,000–4,500 K, the contrast with the surrounding material at about 5,800 K leaves them clearly visible as dark spots.
Sunspot populations quickly rise and more slowly fall on an irregular cycle about every 11 years. Significant variations of the 11-year period are known over longer spans of time. For example, from 1900 to the 1960s the solar maxima trend of sunspot count has been upward; from the 1960s to the present, it has diminished somewhat. The Sun is presently at a markedly heightened level of sunspot activity and was last similarly active over 8,000 years ago.
See below how sunspots have varied over recent years.
*This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article for Sunspots.
Sunspot populations quickly rise and more slowly fall on an irregular cycle about every 11 years. Significant variations of the 11-year period are known over longer spans of time. For example, from 1900 to the 1960s the solar maxima trend of sunspot count has been upward; from the 1960s to the present, it has diminished somewhat. The Sun is presently at a markedly heightened level of sunspot activity and was last similarly active over 8,000 years ago.
See below how sunspots have varied over recent years.
April 29, 2008
April 29, 2005
April 29, 2003
April 29th, 2000
April 29th, 1999
*This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article for Sunspots.
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