By David L. Brown
What is wrong with this picture? It is our Sun, as photographed a few days ago. And what is wrong is that it shows no sign of sunspots, none at all. And that is a cause for curiosity because the low point in the usual 11 year sunspot cycle was supposed to have ended well over a year ago, and yet for day after day, week after week, month after month the Sun continues to present a blank, featureless face to the Universe. The return of spots to the surface of the Sun is now about 18 months past due.
Scientists do not have an explanation for this, but there are historic precedents. During the 17th and 18th Centuries the Sun entered an extended period of quiescence during which virtually no sunspots were observed. Dubbed the Maunder Minimum, the anomalous period lasted from about 1645 to 1715.
Does this mean anything to we humans here on Earth? After all, what difference could it make whether the Sun exhibits spots or appears like a featureless orange ball? Well, it could mean a lot. Many climate scientists relate the Maunder Minimum and other periods of low activity on the Sun with cooling. In fact, the event called the Little Ice Age appeared to be connected in time with the Maunder Minimum, suggesting a correlation between the two.
To understand just how unusual the Maunder Minimum was, during one 30-year period of the event astronomers observed only about 50 sunspots. In modern times, 40,000–50,000 spots would have been observed during that length of time. That represents a reduction on the order of a thousandfold.
Now you may have learned that sunspots are cool eruptions on the surface of the solar disc, so at first glance it may seem that more sunspots, not fewer, would result in cooling. But the areas around a sun spot are hotter than the average surface temperature of the Sun, resulting in a higher total output of radiation.