Observations of 2,700-year-old total solar eclipses provide insight into our ancient solar system
Researchers have returned to records of a rare celestial phenomenon observed in China around 2,700 years ago. By applying modern astronomy methods and measurements to recreate the appearance of the sun in Qufu, the capital of the ancient state of Lu, on July 17, 709 BCE, the team confirmed ancient records of a total solar eclipse and corona.
Reported in Astrophysical journal lettersthe results refine and reinforce the recent reconstructions of the Earth rotation and activity of the sun in the 8th century BCE, suggesting that one was faster while the other was weaker than today as the eclipse approached.
“Some of our ancestors were very skilled observers,” said study author Meng Jin from Lockheed Martin’s Solar Energy and Astrophysics Laboratory, according to a press release. “When we combine their careful recordings with modern computational methods and historical evidence, we can potentially find new information about our planet and star from thousands of years ago.”
Learn more: These 5 ancient cultures believed solar eclipses were omens and prophecies
Extensive eclipse archives
This ancient Chinese text, dating from 709 BCE, is from the Spring and Autumn Annals and contains some of the oldest written records of a total solar eclipse.
(Image credit: National Archives of Japan, CC BY)
In ancient China, strange phenomena in the sky, such as eclipses, aurora borealis, and other oddities, were commonly thought to be omens for the state. This led emperors, their courts, and their courtiers to create comprehensive records of the sky and preserve them over time, leaving China with one of the most complete eclipse records in ancient times.
According to these accounts, something strange was spotted in the skies of Qufu in 709 BCE. Reported in two separate records – a chronicle titled “Spring and Autumn Annals”, compiled approximately two to three centuries after the event, and another chronicle titled “Hanshu”, compiled a few centuries later – the event represents one of the first total solar eclipses and one of the first recorded coronas attributable to an actual date.
“What makes this disk special is not only its age, but also a later addition to the ‘Hanshu’ (‘Book of Han’) based on a quote written seven centuries after the eclipse. It describes the eclipsed sun as ‘completely yellow above and below,'” said Hisashi Hayakawa, another author of the study from Nagoya University, according to the release. “This addendum has traditionally been associated with a record of a solar corona. If this is indeed the case, it represents one of the earliest surviving written descriptions of [a] solar crown.
Learn more: An omen of doom and other myths surrounding solar eclipses
Correction of eclipse coordinates
Turning to Qufu’s coordinates and the methods of modern astronomy to corroborate this information, researchers initially found no evidence of a total solar eclipse. However, after consulting archaeological records and reports, they recognized that their coordinates for Qufu were incorrect, pointing to a location approximately five miles from the ancient city.
By adjusting the coordinates and rerunning the calculations, the team ultimately concluded that a total eclipse had been observed in Qufu in 709 BCE.
“This correction allowed us to accurately measure the Earth’s rotation during the total eclipse, calculate the orientation of the Sun’s rotation axis, and simulate the appearance of the corona,” Hayakawa added in the release.
Learn more: Why astronomy is considered the oldest science
Ancient glimpses of the solar system
Taken together, the results not only clarify the occurrence and timing of the total solar eclipse; they also revise estimates of the Earth’s rotation speed, which was much faster in ancient times, and corroborate estimates of the Sun’s activity, which was also much lower in ancient times.
In fact, although researchers caution that the corona’s later record is somewhat less certain, due to its relative age and lack of certification in similar sources, the shape and structure of the corona—if it actually appeared—suggest that the eclipse occurred after the sun recovered from a period of reduced activity from about 808 BCE to about 717 BCE.
According to the researchers, the results solve several important mysteries about our solar system and the movement and activity of the planets and stars there. They also emphasize that ancient records serve as imperative repositories of astronomical information, providing insight into our world today and thousands of years ago.
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