Sunspot that delivered northern lights is returning. What to know. (2024)

The extreme solar storm originated from an impressive region of sunspots or bruiselike discoloration on the sun that throbs and pulsates with energy. And, after two-plus weeks hidden on the back side of the sun, that same colossal sunspot group is about to point toward Earth once again.

Though the sunspot cluster isn’t as big as it once was, it’s still flaring and hurling magnetic energy into space. Some is expected to sideswipe Earth as soon as Friday night, and more geomagnetic storms — and potential auroral displays — could be in the offing.

The sun is entering its most active period in two decades, launching more intense eruptions from its surface. Even if this aurora show doesn’t pan out, scientists say there will probably be more viewing opportunities over the next year or two.

In early May, a particularly large and complex sunspot cluster called Active Region 3664 appeared on the solar disc. It cranked out a barrage of X-class solar flares — the most intense kind, or explosions of high-energy particles and electrons that race through space at the speed of light. Several shortwave radio blackouts affected high-frequency signals on Earth.

Slower-moving shock waves of magnetism, known as coronal mass ejections (CMEs), barreled through space like interstellar tsunamis. Several overlapped, colliding with Earth’s magnetic field on the night of May 10, igniting vibrant auroral displays around the world. NASA said it was among the strongest aurora displays in 500 years.

Active Region 3664 disappeared from view on May 15, rotating onto the back side of the sun and facing away from Earth. That, at least temporarily, prevented us from being in the line of fire for any of its eruptive explosions.

The sun takes about 27 days to rotate, meaning that, since two weeks have elapsed, the sunspot is rotating back into view. As is customary, it has been assigned a new name and number: Active Region 3697.

“It is not a surprise that it survived rotation around the far side of the sun,” Shawn Dahl, service coordinator at the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center in Boulder, Colo., said in email. “The fact this region … has rotated back into view and is still producing [significant radio blackout] activity is rather unusual.”

There was also a dramatic explosion on the back side of the sun on May 20, and space weather forecasters believe that Active Region 3664 (now 3697) was the culprit.

Already, forecasters at the Space Weather Prediction Center are gearing up for more geomagnetic storming. An X-class solar flare preceded a CME that launched off the southwestern (bottom left) rim of the solar disc on Wednesday. It’s believed that the CME will sideswipe Earth, causing some minor to moderate geomagnetic storming on May 31.

Any storming should reach up to G2 levels on a 1 through 5 scale, according to NOAA, which would make the aurora visible in southern Canada and perhaps the far northern tier of the United States.

The preceding flare actually lasted a remarkably long time — more than an hour — and caused a lengthy shortwave radio blackout over the Americas.

No one can definitively say what’s to come over the next 10 days. The sunspot region will be most pointed toward Earth in the next three to nine days, providing a nearly week-long window during which CMEs could be “geoeffective,” or primed to affect Earth.

Whether the sunspot region coughs, sputters or erupts — and gives us yet another high-end geomagnetic storm — remains to be seen.

Kasha Patel contributed to this report.