Today’s sun is blank like it’s been for much of 2018 as the solar cycle heads toward a 2019-2020 minimum. The fine texture you see is caused by solar granules which are the tops of rising cells of hot plasma. A typical granule is about 1,500 km across and lasts around 10 minutes before cooling and sinking back into the sun. NASA / SDO
It’s been a long time but skywatchers in the northern U.S. states have a shot at seeing the aurora beginning at nightfall tonight through about 1 a.m. (Central Time). We’ve been in a dry spell for northern lights for some time now. That’s not surprising considering that the sun is slouching toward the next solar minimum expected in 2019-2020.
Graph showing the last three solar cycle plotting sunspot numbers. The double peak of the current cycle is shown. You can see there’s been a general decline in solar activity over the past 25 years or so. NASA
Solar activity bounces back and forth between high and low during a cycle that lasts about 11 years. The last maximum occurred in spring 2014 and was one of the wimpiest on record. In fact, it was the least ...