The evidence was locked inside trees for centuries.

For decades, scientists have relied on ice cores and satellite records to reconstruct the Sun’s most powerful outbursts. But a quieter archive has been standing in plain sight. Deep within the growth rings of ancient trees, researchers have identified a chemical signature that points to a sudden, extreme surge of solar radiation. The discovery suggests the event was stronger than many modern flares. What it means for our understanding of solar risk is only beginning to unfold.



