'We'll be studying this event for years': Recent auroras may have been the strongest in 500 years, NASA says

The unprecedented auroras that recently wowed millions of people across the globe were some of the most intense light shows our planet has seen for half a millennium, NASA has revealed. The dancing lights, which may have reached the equator, were triggered by Earth's most powerful geomagnetic storm in more than two decades.

Between May 10 and May 12, our planet experienced a major geomagnetic disturbance after at least five solar storms slammed into Earth back-to-back, temporarily weakening the magnetosphere. The solar storms, known as coronal mass ejections (CMEs), were launched by solar flares from the gigantic sunspot AR3664, which was more than 15 times wider than Earth at the time — the biggest dark patch to appear on the sun for a decade. Several of these solar flares reached "X-class" status — the most powerful type of surface explosion the sun can produce.

The resulting geomagnetic storm was mainly ranked as G4, or "severe," which is the second-highest class of geomagnetic storm. But on two occasions, the storm temporarily reached "extreme" G5 conditions, on par with the fallout from the Carrington event of 1859 — the most powerful solar storm in recorded History, which triggered auroras as far south as Cuba and Hawaii. This was the first time Earth experienced G5 conditions since the Great Halloween storms of 2003.

Fortunately, this superpowered storm did not cause any major issues on Earth apart from some temporary satellite and communications disruptions. However, the event did paint large parts of our planet's skies with vibrant, multicolor auroras as the weakened magnetosphere allowed large amounts of solar radiation to bombard the upper atmosphere and excite gas molecules.

These light shows covered vast areas of both of Earth's hemispheres and were "possibly one of the strongest displays of auroras on record in the past 500 years," NASA representatives wrote in a statement. 

"We'll be studying this event for years," Teresa Nieves-Chinchilla, the acting director of NASA's Moon to Mars Space Weather Analysis Office, said in the statement. "It will help us test the limits of our models and understanding of solar storms."

Related: Why are auroras different colors?