This level of activity is so low, some scientists have suggested we may be entering a "deep" solar minimum, and potentially even a Grand Minimum—the last of which took place in the 17th century and coincided with a mini ice age.

The sun has an 11-year cycle where activity waxes and wanes. This is caused by the strengthening and weakening of its magnetic field. The point when activity is highest is known as the solar maximum, which is characterized by more sunspots appearing on the surface. The solar minimum is where activity falls, and far fewer sunspots appear. The last solar maximum peaked in 2014.

In April last year, scientists at the National Oceanic and Atmospheric Administration predicted the forthcoming solar minimum would be similar to the last cycle. In a statement, Lisa Upton, Ph.D., solar physicist with Space Systems Research Corp, said the next solar cycle would be much like the last, with a weak maximum and a "long, deep minimum." However, she also said there was "no indication" we are approaching a solar minimum in line with the last Grand Minimum—known as the Maunder Minimum.

So far this year, there have been 104 days where no sunspots have appeared on the sun's surface, according to SpaceWeather.com. Across the whole of 2019, there were 281 sunspot-free days. As the website notes, the lack of activity on the sun suggests the solar minimum is taking place. "So far this year, the sun has been blank 76 percent of the time, a rate surpassed only once before in the Space Age," it said. "Last year, 2019, the sun was blank 77 percent of the time. Two consecutive years of record-setting spotlessness adds up to a very deep Solar Minimum, indeed."