The sunspot that brought the northern lights is back. Here’s what you need to know.

An extreme solar storm originates from a striking region of sunspots or bruise-like discoloration on the sun that pulses and pulsates with energy. And after more than two weeks hidden from the backside of the sun, the same colossal group of sunspots is about to point toward Earth again.

Although the sunspot cluster is not as large as it once was, it is still blazing and spewing magnetic energy into space. Some are expected to make landfall as soon as Friday evening, and more geomagnetic storms – and potential auroral events – could be on the way.

The sun is entering its most active period in two decades, triggering more intense eruptions from its surface. Even if this glow show fails, scientists say there will likely be more viewing opportunities in the next year or two.

A massive sunspot cluster

In early May, a particularly large and complex sunspot cluster called Active Region 3664 appeared on the sun’s disk. It triggered a barrage of X-class solar flares, the most intense type, or explosions of high-energy particles and electrons that race through space with the speed of light. Several shortwave radio blackout interruptions affected high-frequency signals on Earth.

Slower-moving shock waves of magnetism, known as coronal mass ejections (CMEs), spread 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.

The sunspot cluster is back

Active region 3664 disappeared from view on May 15, rotating to the back of the sun and facing Earth. This, at least temporarily, prevented us from being in the line of fire for any of his eruptive explosions.

The sun takes about 27 days to rotate, meaning that after two weeks have passed, the sunspot rotates back into view. As usual, it got a new name and number: Active Region 3697.

“It’s no surprise that it survived a spin around the far side of the sun,” Sean Dahl, service coordinator at the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center in Boulder, Colorado, said in an email. “The fact that this region … has come back into view and is still producing [significant radio blackout] the activity is quite unusual.

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

Forecasters at the Space Weather Prediction Center are already preparing for new geomagnetic storms. An X-class solar flare preceded the CME that launched from the southwest (lower left) edge of the sun’s disk on Wednesday. The CME is expected to hit Earth sideways, causing a small to moderate geomagnetic storm on May 31.

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

The previous eruption actually lasted a remarkably long time — more than an hour — and caused a prolonged shortwave radio blackout over America.

No one can say for sure what will happen in the next 10 days. The sunspot region will be most pointed toward Earth for the next three to nine days, providing a nearly week-long window during which CMEs can be “geoeffective,” or poised to impact Earth.

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

Kasha Patel contributed to this report.