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The sun once was considered a steady star without change. The sun's energy output, as measured above the earth's atmosphere, was called “the solar constant.” As astronomers studied the sun, they realized that this notion wasn't quite correct. They found that the solar output varied slightly by a few tenths of a percent. The amount rose when the sun was active (solar maximum) and declined when it was quiet (solar minimum).

Solar astronomers counted the number of dark spots on the disk of the sun to gauge the sun's activity. In 1843, a German amateur astronomer, Samuel H. Schwabe, realized that the number of sunspots varied over time. The average cycle goes from a few to many spots and back in about 11 years. A few years later, Rudolph Wolf, a Swiss astronomer, confirmed the roughly 11-year cycle. He numbered the sun spot cycles beginning in 1755 as Cycle Number One. In 1852, four astronomers realized that the activity of the sun and the geomagnetic activity on earth were interrelated. That was the beginning of the sun-earth connection and space weather.

Most astronomers believe that the sun has completed our latest cycle and has begun Cycle Number 24. It's not clear exactly when the new cycle began. Solar forecasters in early 2006 predicted that Cycle 23 would end in late 2006 or early 2007, with a quick return to a very active or perhaps record solar maximum in 2010 or early 2011. But the sun didn't get the memo. The solar minimum for Cycle 23 dragged on. The slumbering sun was not roused through 2008. In fact, the quiet sun in 2008 set some impressive records. For example, there was a 50-year low in solar wind pressure and a 12-year low in solar irradiance, resulting in a 6 percent drop in ultraviolet light.



As 2009 began, the sleepy sun was not showing any signs of waking. New predictions in early 2009 shifted the maximum of Cycle 24 to 2012. By May 2009, it was clear the sun still wasn't acting according to plan. Cycle 24 maximum is now predicted to occur in May 2013.

The sun in 2009 was nearly as sluggish as in 2008. It was clear that Cycle 23 would not last the average 11 years, but perhaps 13 years plus a few months.This would place Cycle 23 just behind the 13 year 8 months of Cycle 4 from 1784 to 1798.

Why does anyone care if sunspot Cycle 23 was very long? First, long cycles have been rare since 1913 (Cycle 15) began a string of less than 10.5 year cycles. Cycle 23 stands out as an unusually long and quiet sun after several very active cycles. During the last nine sunspot cycles from 1913 to 2009, only two were longer than 10.5 years. Contrast that with Cycles 1through 14, with 11 cycles lasting more than l0.5.

Second, the unexpected long Cycle 23 shows that we have lots to learn about the sun. Astronomers have observed a very active sun in the last few decades and have assumed that great activity would continue with a few minor corrections. Then along came Cycle 23 and the sun took a snooze.

Third, solar activity may affect earthly climate in ways not fully understood. Low sunspot counts over extended periods may be correlated with periods of cooling and harsh winters in the Northern Hemisphere. But some scientists dispute this idea, arguing that other causes, such as volcanic eruptions, are more likely for the cooling. The scientific jury is still out on this one.

What's going on with the sun lately? Since December 2009, the sun has stirred. Scientists have observed few spotless days, several prominent sun spot groups and the highest sun spot numbers since June 2007. Is this the beginning of increased activity of Cycle 24? Most likely. However, recent unpredictable solar activity makes it difficult to say.

The sun had one month of modest activity during April 2008 and then returned to sleep for more than a year. But if December 2009 and January 2010 sunspot activity is a guide, the sun has begun to wake up. What the sun does in 2010 will be interesting to watch. Stay tuned to the Umpqua StarGazer for updates.

Roseburg resident Paul Morgan has been a stargazing fan since his boyhood days in the 100 Valleys of the Umpqua.