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large sunspot Plot Sunspots since 1755
This site allows you to plot 11 years worth of sunspot numbers centered on any date between 1755 and the present. Great for retrieving sunspot data!
The Spinning Sun
An activity for you to determine the solar rotation rate based upon the movement of sunspots.
The Sunspot Cycle
Daily observations and counts of sunspots were started at the Zurich Observatory in 1749 and, with the help of other observatories, continuous observations have been obtained since 1849. Monthly averages of the sunspot numbers show that the number of sunspots visible on the Sun waxes and wanes with an approximate 11-year cycle. Visit this site to find graphs and charts of sunspot activity, including current ones updated monthly. Note, however, that the "Sunspot Number" referred to in these graphs is not a count of sunspots, but rather a number adjusted to take into account the number of groups visible, the number of individual spots visible, and differences between observers. The next reference describes how the number is determined. By David H. Hathaway of the NASA/Marshall Space Flight Center.
sunspot collection What is the Sunspot Number?
The abundance of sunspots on the Sun varies on timescales from a few hours to many years. Historically, an index called the 'sunspot number' has been used to quantify the abundance of spots. The index is still in wide use today. This site explains how the "sunspot number" is computed.
sunspot closeup Want to track solar activity?
The Paderborn Public Observatory in Germany hosts a non-profit amateurs club whose main activity is solar observation. The club has established the INTER-SOL Programme (ISP) which is an addition to, but different from, the usual method of monitoring and classifying sunspots. About 50 stations, amateurs as well as professionals throughout the world contribute their data to INTER-SOL.
sunspot prediction chart Sunspot Cycle Predictions
Several techniques are used to predict the amplitude of a sunspot cycle during the time before sunspot minimum. Relationships have been found between the size of the next cycle maximum and the length of the previous cycle, as well as the level of activity at sunspot minimum and the size of the previous cycle. Among the most reliable techniques are those that use the measurements of changes in the Earth's magnetic field at, and before, sunspot minimum. These changes in the Earth's magnetic field are known to be caused by solar storms but the precise connections between them and future solar activity levels is still uncertain. Marshall Space Flight Center
Galileo's View of Sunspots
Galileo was not the first to observe sunspots (the Chinese earned that distinction thousands of years before), but Galileo was the first to study sunspots and their movements through a telescope. He carefully sketched what he saw. Some refuted his drawings, claiming the black spots were unknown planets crossing the disk. But Galileo was able to prove the spots were on the Sun (see Galileo's Proof and that of another scientist Wilsons Proof).
Mt. Wilson sunspot sketch Daily Sunspot Sketchs at Mt. Wilson

Take the Sunspot Quiz!

These sets of questions test your knowledge of sunspots.

Image Credits: 1 - Large sunspot image taken by MDI on the SOHO spacecraft.
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