Most years, the Sun produces hundreds or thousands of sunspots – magnetic storms that look like dark splotches on its surface. From 1645 to 1715, though, sunspots all but disappeared. In many years, the number stayed in the single digits. And in some years, there were no sunspots at all.

Today, that period is known as the Maunder minimum. It’s named for British astronomer Edward Maunder, who was born 175 years ago today. He wrote about the period in the late 1800s.

Maunder was working at Britain’s Royal Observatory. He was assisted by his wife, Annie, who was a “computer” at the observatory – someone who did the tedious calculations.

Maunder discovered a pattern in the sunspots, which wax and wane during a cycle of about 11 years. When a new cycle begins, most of the sunspots are concentrated at the Sun’s middle latitudes. As the cycle peaks, they’re concentrated closer to the equator.

But he’s best known for the Maunder minimum. It occurred during the “Little Ice Age” – a period of unusual cold. That suggests a link between solar activity and Earth’s climate. But the link isn’t confirmed – it could be just a coincidence.

We still don’t know what caused the sunspots to vanish. It had happened at least once before. So the mystery of the Maunder minimum remains unsolved.

Script by Damond Benningfield