This Star Could Help Explain Why Our Sun Paused Its Cycle For 70 Years

Our sun had very few sunspots for 70 years and this period of "solar calm" remains a mystery to this day. Scientists have now identified a star that seems to be behaving the same way, opening an opportunity to understand why the phenomenon happened in our host star.

Sunspots are the regions on the surface of the sun that are darker because they are cooler than the other areas. However, they are still very hot at around 6,500 Fahrenheit and are actually associated with solar activity, resulting in solar flares and sometimes even coronal mass ejections.

During the sun's 11-year solar cycle, there are fewer sunspots during the solar minimum and more sunspots during the solar maximum. Scientists are on the lookout for these features to predict solar storms and other solar events that may end up interfering with systems on Earth.

Astronomers have been watching out for the changes in sunspots since the 1600s, Pennsylvania State University (PSU) noted in a news release. However, from the mid-1600s to the early 1700s, there was a 70-year period, called the Maunder Minimum, wherein the solar activity was "very low" and constant instead of periodic, researchers said in their new study published in the Astronomical Journal. There were "very few" sunspots during this period of "solar calm" from 1645 to 1715.

"We don't really know what caused the Maunder Minimum, and we have been looking to other sun-like stars to see if they can offer some insight," study first author Anna Baum, who was with PSU at the time of the study, said in the news release.

For their work, the researchers looked at five decades of data measuring 59 sun-like stars. They identified 29 that have starspot cycles much like our sun, some that didn't have cycles possibly because they are spinning too slowly or are "magnetically dead," and others that still need further observations to determine if they have a cycle, PSU noted.

However, one of the stars seems to be a good Maunder minimum candidate. Called HD 166620, it has a cycle period of about 17 years but it seems to have paused the cycle. It has entered a period of low activity but has so far not shown signs of starspots since 2003.

Although there have been concerns initially among the researchers that there may be a mistake, further analysis concluded that the star has "stopped cycling," study author Jacob K. Luhn, who is now with the University of California, Irvine, said in the news release.

The scientists hope that they will be able to watch it during the rest of the odd period and when it begins to cycle again. This could shed light on what caused the phenomenon in our own star.

"Did the sun's magnetic field basically turn off? Did it lose its dynamo? Or was it still cycling but at a very low level that didn't produce many sunspots?" Baum said. "We can't go back in time to take measurements of what it was like, but if we can characterize the magnetic structure and magnetic field strength of this star, we might start to get some answers."