Every 11 years, activity on the Sun peaks. More sunspots, prominences, flares, and other phenomena are seen on our star’s face, plus, there’s an uptick in visible aurorae here on Earth. This time period is called the solar cycle, and we’re in the middle of the peak of the current one, solar cycle 25. These periods are not exactly 11 years long. They vary in length from 8 to 14 years, with the average being 10.7 years.
Some history
Although the repeating cycle of sunspots was first seen in the mid-18th century, the fact that the Sun went through cycles was first identified by the German amateur astronomer Samuel Heinrich Schwabe in 1843. Based on his 40 years of observations, Swiss astronomer Rudolf Wolf assigned the designation of solar cycle 1 to the cycle that began in February 1755. Wolf also created the way we still designate sunspots, so the daily number of them is now called the Wolf number.
Not-so-active times
Solar activity, measured mainly by sunspot numbers, has dipped for long periods in the past 3,000 years. Even before people started doing sunspot counts, however, scientists are able to measure solar activity by studying tree rings and elemental deposits on Earth.
The first so-called grand solar minimum of the six recognized within this time period is the Homeric Minimum, which lasted from about 800 BC until 600 BC. Others have lasted between 40 and 150 years. During such times, sunspots are rarely seen on the Sun.
Observe — safely
But this is not one of those times. In fact, for the past several years sunspot counts have been strong and amateur astronomers have seen, or photographed, many nice displays. Observing the Sun is easy, but it can be dangerous unless you have a proper filter. Prior to solar eclipses, eclipse viewing glasses are sold and given away by the millions. These cardboard glasses have special Mylar lenses that reduce the Sun’s light to a safe level for human eyes. For a quick, non-magnified, look at the Sun you can use one of them.
But you won’t see any sunspots unless one happens to be about twice the diameter of Earth. Such spots do appear, albeit rarely. For a better view, point a telescope with an approved solar filter — attached to its front — at the Sun. Then you can change magnifications by simply switching eyepieces, just like you do when you’re observing a nighttime celestial object. Remember, though, the filter always goes at the front of the optics you’re using — your eyes, binoculars (you’ll need two filters), or a telescope. By observing the Sun, you’ll effectively double the use of your telescope. Good luck!
