Last month, the massive, hot ball of glowing hydrogen and helium at the center of our solar system—otherwise known as our sun—released its largest solar flare since October 2017. Although it’s too early to know for certain, NASA says in a statement that this new activity might indicate that the sun is “waking up” from its cyclical slumber.
As Hannah Osbourne reports for Newsweek, activity on the sun’s surface increases and decreases according to a roughly 11-year cycle, although that can vary. During the period known as the solar minimum, the sun has few sunspots and decreased surface activity; during the solar maximum, on the other hand, sunspots and solar flares tend to be plentiful. The last solar maximum peaked in 2014, per Newsweek, so scientists expect the sun to reach its solar minimum soon, although it’s difficult to predict exactly when.
As Victoria Jaggard reported for Smithsonian magazine in 2014, a solar flare is a burst of radiation that occurs when a magnetic energy releases from the outermost part of the sun’s atmosphere, also known as its corona. This extremely hot layer burns at more than one million degrees Celsius, Nicholas St. Fleur reported for the New York Times in 2017. Flares on the sun’s surface are associated with sunspots, which are cooler patches on the sun’s surface that appear as dark spots and form where magnetic fields on the sun’s surface are strongest, according to Smithsonian.
According to a video from NASA's Goddard Space Flight Center, sunspots also change locations on the sun as it goes through its cycles of activity. Sunspots appear more frequently at middle latitudes during solar maximum, and closer to the equator during solar minimum.
This most recent flare, which took place on May 29 at 3:24 a.m. Eastern time, was an M-class flare: relatively small compared to the two X-class flares let off in 2017, but significant considering that it’s the first of its size in two years. This flare was too weak to warrant an alert from NOAA’s Space Weather Prediction Center. Scientists will be watching to see whether more activity on the sun’s surface follows this one. Solar minimum can only be determined in hindsight—it takes about six months to officially determine when the sun has passed through its period of least activity and started picking up steam, according to the statement.
“The sunspots may well be harbingers of the Sun's solar cycle ramping up and becoming more active. Or, they may not. It will be a few more months before we know for sure,” said NASA in the statement.