Sun was once very quiet for 70 years. A nearby star may explain the reason for this.

(ORDO NEWS) — Over a long enough period of time, our Sun is quite predictable. Approximately every 11 years, it goes through a cycle of high and low activity, the latter characterized by an increase in the number of sunspots, flares and coronal mass ejections.

From cycle to cycle, it is difficult to predict what period of activity our Sun will go through, but there is always an increase in activity to a maximum and a decrease to a minimum.

Well, almost always. In the 17th century, the Sun went through a period when there were almost no spots on it. From 1645 to 1715, this period spanned several solar cycles and is known as the Maunder minimum.

This strange irregularity has puzzled scientists for a long time; now the answer to this question can be given by another nearby star. It appears to have fallen into a similar dormant period and watching what it does may help us understand what the hell our own Sun is up to.

“We don’t know what caused the Maunder Minimum, and we’ve looked to other Sun-like stars to see if they can offer any insight,” says physicist Anna Baum, formerly of Pennsylvania State University and now at University of Lehi.

“We have identified a star that we believe has entered a state similar to the Maunder Minimum. It will be very interesting to continue observing this star during and hopefully as it emerges from this minimum, which can be extremely informative regarding activity Sun 300 years ago.

The solar cycle is based on the magnetic field of the Sun, created as a result of the action of the dynamo process in the interior of the star.

Every 11 years, the sun’s magnetic field flips, with the north and south magnetic poles swapping. Astronomers have been observing sunspots since about 1610, including Galileo Galilei, and the first recorded solar cycle began in 1755.

A solar minimum – characterized by a minimum level of sunspot and flare activity – marks the end of one cycle and the beginning of a new one, and occurs when the Sun’s magnetic field is at its weakest.

This is because the Sun’s magnetic field controls its activity: sunspots are temporary regions of strong magnetic fields, and coronal mass ejections and solar flares result from energy releases when magnetic field lines tangle, break, and reconnect. Therefore, when the magnetic field increases, it is quite logical that solar activity increases.

Point activity has also been observed in other stars, although our records of these stars are not so distant in time. Baum and her colleagues collected data from several sources on the stellar activity of 59 stars over several decades.

Of these, 29 stars showed distinct star formation cycles similar to those we observe on the Sun. The rest of the stars did not show any stellar activity at all, which suggested that their rotation might be too slow for dynamo processes, and for some, there was simply not enough data to draw a conclusion.

And of those 29 stars, one stood out: HD 166620, located 36 light-years away. This star is about 80 percent of the size and mass of the Sun and is about 6 billion years old (compared to the Sun’s 4.6 billion years). It appears to have a cycle of about 17 years, but there has been absolutely no sign of sunspots since 2003.

“When we first saw this data, we thought it must have been a mistake, that we put data together for two different stars, or there was a typo in the catalog, or the star was misidentified,” says astrophysicist Jacob Lun, a former collaborator University of Pennsylvania and now at the University of California, Irvine.

“But we checked everything twice and thrice. The observation time corresponded to the coordinates that we expected to see the star.

And there are not many bright stars in the sky that Mount Wilson observed. No matter how many times we checked, we always came to the conclusion that this the star just stopped cycling.”

This means that it can also experience a Maunder minimum. Unfortunately, the beginning of this period of low activity occurred during a break between observations of the star; but continued observations of the star during the entire period of low activity may help shed light on the strange activity of our Sun.

“There is a lot of discussion about what the Maunder minimum is,” Baum said.

“Did the Sun’s magnetic field turn off? Did it lose its dynamo? Or did it keep cycling, but at a very low level that didn’t produce a lot of sunspots?

We can’t go back and measure how it was, but if we can characterize the magnetic structure and magnetic field strength of this star, we can get some answers.”

This, in turn, could help us better understand solar weather, which has important implications for the Earth and the rest of the solar system. And it can help us better understand how the stars work: what drives them and what goes on in their mysterious hearts.


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