Korea's ancient auroras and Nuri's new insights

If a time machine existed, one might wish to travel back and tell them what their work would eventually make possible.

Moon Hong-kyu

The author is a principal researcher at the Korea Astronomy and Space Science Institute.

Historical records show that unusual lights once appeared over Korea’s night sky. The Annals of King Injo report that on Jan. 8, 1624, at “around 3 a.m., a light-like glow appeared in the southeast, and from 4 to 5 a.m. it reappeared in the northeast, southeast and southwest.” On March 4, 1626, court astronomers again observed “light-like glows” in the northeast and northwest early in the evening. As these entries coincide with heightened solar activity, they were likely sightings of auroras. One can imagine the astonishment of those who watched curtains of shifting color reach as far south as the Korean Peninsula. This writer has never seen such a display and knows it only through science.

The northern lights, seen here from Perseverance Trail near downtown Juneau, Alaska, pulsing above the Juneau Ridge on Nov. 12. [AP/YONHAP]

The sun constantly releases high-energy particles, which are deflected by Earth’s magnetic field. But the balance changes when the sun emits a burst of particles, much like droplets expelled by a sudden sneeze. A strong solar storm can overwhelm the magnetic field, causing stored energy to break out. Earth’s magnetic field resembles stretched strands of rubber. When those strands snap and reconnect, particles surge outward and collide with the atmosphere, generating vivid light.

The magnetic poles, shaped like the stem and base of an apple, absorb the brunt of this bombardment. Oxygen atoms emit green and red light when energized, while nitrogen molecules glow purple. These colors blend to illuminate the night sky in striking patterns. This is the mechanism behind an aurora.

Korea’s most recent space mission now offers a new window into that process. The fourth launch of the Nuri rocket carried the Next-Generation Medium-Sized Satellite No. 3, equipped with “ROKITS,” an aurora-monitoring camera developed by the Korea Astronomy and Space Science Institute. The system captures green, red and full visible-band wavelengths, allowing researchers to determine where auroras form and how their shapes evolve over time.

Four centuries ago, court astronomers observed the sky from the ground and recorded what they saw with brush and ink. Their successors now observe the same sky from 600 kilometers above Earth, looking down from orbit to study the physics of the aurora with modern instruments. If a time machine existed, one might wish to travel back and tell them what their work would eventually make possible.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.