OIST Detects 1200-1201 Solar Proton Event 10-30% of Extremes, Sharpening Astronaut Risk Models
Updated
Updated · Earth.com · May 22
OIST Detects 1200-1201 Solar Proton Event 10-30% of Extremes, Sharpening Astronaut Risk Models
3 articles · Updated · Earth.com · May 22
A carbon-14 spike in tree rings dated to winter 1200 through spring 1201 revealed a mid-range solar proton event that older methods could not detect.
OIST's higher-precision technique found the signal in buried asunaro logs from Aomori, while medieval Chinese records of low-latitude red auroras helped confirm the timing.
The result also showed Fujiwara no Teika's 1204 Kyoto red-sky diary entry did not match a major solar event, shifting the likely storm window a few years earlier.
Year-by-year measurements suggest the Sun around 1200 cycled every 7-8 years rather than today's roughly 11, pointing to a more intense period with some unexpected auroras near solar lows.
Events at 10-30% of the largest known storms can still endanger astronauts beyond Earth's magnetic shield, giving Artemis-era planners a better baseline for how often hazardous mid-size outbursts occur.
Medieval 'red sky' diaries helped uncover a giant solar storm. What other cosmic secrets are waiting to be found in historical records?
The Sun's cycle was once shorter and more intense. Could this chaotic solar behavior return and threaten our technology-dependent world?
An 800-year-old storm was 14 times stronger than modern ones. Are Artemis astronauts prepared for the Sun's forgotten fury?
The Medieval Solar Storm of 1200-1201 CE: Breakthroughs in Detection, Climate Impact, and Space Weather Preparedness
Overview
A groundbreaking study led by Hiroko Miyahara and her team, published in April 2026, revealed new insights into the Sun's behavior during the Medieval Period by analyzing tree-ring carbon-14 data alongside historical records. Trees absorb carbon dioxide, which includes carbon-14 produced when cosmic rays interact with Earth's atmosphere. By measuring carbon-14 in tree rings, the researchers identified intense solar activity between 1190 and 1220 CE. This discovery not only helps reconstruct ancient solar storms but also highlights the Sun's potential impact on Earth, emphasizing the importance of understanding past solar events to assess modern space weather risks.