Fresh take: The blank sun, what on earth is happening?

The blank solar disk in white light.

SEDONA — For most of last week the sun has been blank, devoid of sunspots.

For the last three years the sun has appeared this way 73 percent of the time; until recently, when we witnessed the arrival of several large sunspots.

Most notably were sunspots AR 2781, AR 2786, AR 2790, AR 2792 and AR 2793.

Nearly all came into view mid-December. Only AR 2781 became visible in late November. Because of their polarity, all of them showed to be members of new solar cycle 25.

The arrival of these sunspots caused some excitement, as it appeared that the sun was becoming active once again.

As we study these sunspots, we notice one thing that they all share in common ... the sun’s southern hemisphere. Scientists have long known that the northern and southern hemispheres on the sun can behave quite differently. One hemisphere can become active while the other can be quiet and calm.

Sunspots AR 2781 and AR 2786 were very large, the others were somewhat smaller. But even a small one like AR 2790 can surprise us.

On Nov. 29 last year this ordinary looking sunspot unleashed an M-class solar flare! Then on Dec. 7, AR 2790 unleashed a C7-class Coronal Mass Ejection (CME) directly toward the earth. X-rays from this flare ionized the top of earth’s atmosphere, causing minor short-wave radio blackouts over South America. Frequencies affected were mostly below 10 MHz. Some ham operators reported that they could actually hear the sound of the flare on their radios!

Studies have suggested that there has been a steady decline in sunspot numbers. At times of solar maximum, literally hundreds of sunspots can appear on the surface of the sun at any given time.

But when there are few or none, it has been suggested that we experience a cooler earth.

The Little Ice Age on earth coincided with what is called Maunder, a minimum 70-year period beginning in the year 1645 when no sunspots were reported at all.

Generally speaking, the sun holds sunspot activity in 11-year cycles. This cycle heralds a quiet sun followed by a sun that shows increased sunspot activity. The English astronomer Edward Maunder suggested that although 11-year cycles have been observed, each is unique and can vary in time length greatly.

The study of sunspots is important — our entire solar system receives its light from the sun.

Understanding sunspots, or their lack of, gives us insight into the workings of our nearest star. What happens in and on the sun has a direct effect on our weather patterns here on earth. How sunspots are formed, their cycles, and their intensity not only educates us on what other similar stars might behave like, but also what these solar cycles might mean for life on earth.

Again, I must state: specially filtered telescopes must be used to study the sun. Be absolutely sure of what you are doing or be with someone who does.

Damage to your eyes can occur in an instant if you are not careful!

Former Arcadian Victor C. Rogus (F.R.A.S.) is a fellow of the Royal Astronomical Society, London, living in Sedona, Arizona.


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