Sun unleashes biggest flare since 2017. Is our star waking up?

On the upper left side of this image from May 29, 2020, from NASA's Solar Dynamics Observatory — shown here in the 171-angstrom wavelength, which is typically colorized in gold — one can see a spot of light hovering above the left horizon. This light emanates from solar material tracing out magnetic field lines that are hovering over a set of sunspots about to rotate over the left limb of the sun. (Image credit: NASA/Solar Dynamics Observatory/Joy Ng)

The sun may be coming out of its slumber at long last.

On Friday morning (May 29), our star fired off its strongest flare since October 2017, an eruption spotted by NASA's sun-watching Solar Dynamics Observatory (SDO).

Today's flare was an M-class eruption, so it was no monster. (And it wasn't aimed at Earth, so there's no chance of supercharged auroras from a potential associated coronal mass ejection of solar plasma.) But the outburst could still be a sign that the sun is ramping up to a more active phase of its 11-year activity cycle, NASA officials said. If that's the case, the most recent such cycle, known as Solar Cycle 24, may already have come to an end.

Scientists peg the start of new cycles at "solar minimum," the time when the sun sports the fewest sunspots and the least activity.

"However, it takes at least six months of solar observations and sunspot-counting after a minimum to know when it's occurred," NASA officials wrote today in an update announcing SDO's flare detection.

"Because that minimum is defined by the lowest number of sunspots in a cycle, scientists need to see the numbers consistently rising before they can determine when exactly they were at the bottom," the officials added. "That means solar minimum is an instance only recognizable in hindsight: It could take six to 12 months after the fact to confirm when minimum has actually passed."

So, stay tuned! More observations should tell us if we're already in Solar Cycle 25.

Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.

Michael was a science writer for the Idaho National Laboratory and has been an intern at Wired.com, The Salinas Californian newspaper, and the SLAC National Accelerator Laboratory. He has also worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz.