Ancient Solar Flare Sheds Light On How Nordic Seafarers Became The Vikings

Evidence from historical solar storms and flares is now being used to improve radiocarbon dating analysis and its having a huge impact on our understanding of the past.

Russell is a Science Writer with IFLScience and has a PhD in the History of Science, Medicine and Technology

Dr. Russell Moul

Russell is a Science Writer with IFLScience and has a PhD in the History of Science, Medicine and Technology

Dr. Russell Moul

Science Writer

Russell is a Science Writer with IFLScience and has a PhD in the History of Science, Medicine and Technology.

Science Writer

A photo of a Viking longboat heading towards a sunset.

We know the Vikings were traders and explorers before they were raiders, but until recently we did not know what caused them to set sail in the first place. Now evidence from historical solar storms is helping us fill in the gaps. Image credit: ajt/Shutterstock. 

As much as they are a staple feature of modern pop culture, there is still much we do not know about the Northern European travelers who became known as the Vikings. In particular, until recently, scholars have struggled to identify a reason why a disparate bunch of Scandinavian farmers transformed into fierce raiders and extensive travelers in the space of a few decades. 

What caused these famed people to set out on a life of exploration and occasional violence? To answer this question, archaeologists and medieval scholars have started turning to an unlikely source for additional information – the Sun.


The birth of the Viking Age?

The Vikings are a tricky subject for historical analysis. There is no denying the impact they had on the early medieval world – but because of centuries of storytelling, misconceptions, mythology, and political appropriation, the idea of the Vikings as hypermasculine blood thirsty raiders has become the predominant image we have today. The situation is not helped by the fact that the Vikings themselves – defined here as scattered groups of people from Scandinavia – were largely illiterate, so left few written records related to their early activities. 

As such, much of what we do know comes from second-hand reports, most of which were produced by Christians who benefited from portraying them as violent pagans. But this idea is inaccurate. Instead, scholars believe the impetus for Viking expansion and exploration was initiated by the need for trade, especially for silver. According to this explanation, the Vikings took part in the growing trade networks that expanded from the Middle East through Russia. 

This expansion was the result of the rising influence of the Islamic empire that would eventually help connect trade networks that connected Europe to North Africa, the Middle East, and even parts of Asia. However, research conducted over the last few years has challenged this interpretation. It seems there is evidence that the Vikings had already established extensive trade networks decades before impulses from the Middle East caused further expansion. 

In 2021, Søren Sindbæk and his colleagues at Aarhus University in Denmark reconstructed the timings of some of the Vikings’ earliest voyages by assessing evidence produced by a massive solar flare that occurred in 775 CE. This flare has helped improve radiocarbon dating techniques that they have applied to artifacts found at an excavation site in Ribe, Denmark. 


This site represents one of the first “cities” of the Viking Age and is located in a place where no one had ever established a settlement like it before. Previous research had shown that there were permanent structures at the site no later than the 720s CE. This suggests that people lived here on a permanent basis, rather than using it as a seasonal site, and, more importantly, that it was a centre of trade and craftsmanship. But prior to Sindbæk and colleagues’ work, it was not easy to establish a solid timeline for this city’s development. That’s where the Sun comes into play.

"The applicability of radiocarbon dating has hitherto been limited due to the broad age ranges of this method. Recently, however, it has been discovered that solar particle events, also known as Miyake events, cause sharp spikes in atmospheric radiocarbon for a single year. They are named after the female Japanese researcher Fusa Miyake, who first identified these events in 2012. When these spikes are identified in detailed records such as tree rings or in an archaeological sequence, it reduces the uncertainty margins considerably," Bente Philippsen, lead author of the study explained in a statement.

By applying an improved calibration curve, based on annual samples, the team was able to identify evidence of the 775 CE Miyake event in one layer at the Ribe site. This provided a kind of chronological anchor point from which they could create an entire sequence of layers and 140 radiocarbon dates around this single year. 

"This result shows that the expansion of Afro-Eurasian trade networks, characterised by the arrival of large numbers of Middle Eastern beads, can be dated in Ribe with precision to 790±10 CE -- coinciding with the beginning of the Viking Age. However, imports brought by ship from Norway were arriving as early as 750 CE," said Professor Sindbæk.


The creation of this new calibration curve is a game changer. It allows archeologists to gain a far greater image of historical time for periods and societies where we lack written records that date specific finds. It also represents the fruits of a huge collaborative effort that was years in the making. 

"The construction of a calibration curve is a huge international effort with contributions from many laboratories around the world. Fusa Miyake's discovery in 2012 has revolutionized our work, so that we now work with annual time resolution. New calibration curves are recurrently released, most recently in 2020, and Aarhus AMS Centre has contributed significantly. The new high-resolution data from the present study will enter into a future update of the calibration curve and thus contribute to improve the precision of archaeological dates worldwide. This will provide better opportunities to understand rapid developments such as trade flows or environmental change in the past," said Jesper Olsen, Associate Professor at Aarhus AMS Centre.

Exploration into the New World

This use of solar activity as a historical marker has not been limited to analysis of the Ribe site either. Again in 2021, another team of researchers published a study showing that, by assessing evidence of a supermassive solar storm that occurred in 992 CE, it is possible to establish a date for when Vikings arrived in America. 

Today, we are familiar with the fact that the Vikings were the first Europeans to arrive in North America. Centuries before Christopher Columbus made his famous discovery in 1492, they had already settled in Newfoundland. However, exactly when they managed to arrive has long been a mystery. Archaeological evidence provided less than precise information while Icelandic Sagas, one of the few forms of in-depth writing related to Norse culture and history, were compiled centuries later and often embellished with fictional details. 


But the research, published in the journal Nature, pinpointed an exact date for Viking presence in North America – 1021 CE. This date stands as the earliest known crossing of the Atlantic by Europeans.  

“Vikings were present in Newfoundland in AD 1021,” confirms the study. “Our new date lays down a marker for European cognizance of the Americas, and […] provides a definitive tie point for future research into the initial consequences of transatlantic activity, such as the transference of knowledge, and the potential exchange of genetic information, biota, and pathologies.”

This discovery was only possible because evidence of the solar storm present in tree rings was also identifiable in wooden artifacts left at the Viking sites in Newfoundland.

The use of this new type of analysis is extremely promising for the future. It means we have a strong chronology for activities in the Viking Age that were previously hard to pin down. Further analysis of other cosmic-ray events will help archaeologists shed new light on other historical dark spots.


  • tag
  • exploration,

  • solar storm,

  • history,

  • solar flares,

  • vikings