Then, 2 centuries later, German amateur astronomer Heinrich Schwabe made an extraordinary discovery during a lengthy search for a planet inside Mercury’s orbit. Schwabe noticed that his observations of sunspots seemed to show a peak about once a decade. For obscure historical reasons, astronomers slapped the label of “solar cycle 1” on an uneventful cycle that peaked in 1760.
Since then, observers have watched 23 cycles come and go. “In March 2007, I predicted cycle 24 would be at least a year late,” says UCLA solar physicist Roger Ulrich, who also began observing the Sun in 1986. “We’ve beat the 1905 extended solar minimum. The end of the Maunder minimum was the last time we had a cycle this long. But I think we’re [now] coming into a period of rising solar activity.”
This anomalously long solar minimum raises the question of whether solar scientists actually understand the Sun’s inner workings. “If you don’t worry about the magnetic fields, we do,” says Ulrich. “The magnetics is where the big puzzle is these days.”
Solar scientists understand that solar magnetic fields start in the Sun’s interior. Dynamic flows of plasma generate electrical currents that give rise to the Sun’s active dynamo. This internal process gives birth to magnetic fields.
The Sun concentrates these fields, twisting and turning them in the process. Such distorted fields inhibit the ability of rising and falling gas cells to transport energy, a process scientists call convection. Where the magnetic fields break through the solar surface, or photosphere, temperatures can be as much as 2700° Fahrenheit (1500° Celsius) cooler than their surroundings. Such a region radiates less energy and looks darker — and we see a sunspot.