The unforgotten sisters: Sonduk, the astronomer queen

Will I ever know the truth about the stars?

I’m too young to engage in theories about our Universe.

I just know that I want to understand more. I want to know all

I can. Why should it be forbidden?

This sentence, found on a votive jar dedicated to her grandmother, had been written by a young girl, a Korean princess of the Silla Dynasty, when she was 15 years old. Her name was Sonduk, but it is also written as Sondok or Seondeok, and she was very interested in astronomy in an era where no education was granted to women. Nevertheless, she became a queen and could pursue her astronomical passion, at least in a certain sense. But let’s go in order.

She was born in 610 CE, and later became the first female monarch of Korea, ruling her country for 14 years. Jinpyeong, her father, was the king of Silla, a kingdom that was born as a city-state in 57 BCE and grew into a kingdom in about 350 CE. The king had no male heirs, so the choice fell on his daughter Sonduk.

This young princess had a brilliant mind, evident from a very young age. At seven, for example, a box of peony seeds arrived at the Court, from China. It had been sent with an accompanying painting that showed what the flowers looked like. Sonduk, looking at the picture, remarked that the flower was pretty, but it was a pity that it did not smell. When asked why, she answered: “If it did, there would be butterflies and bees around the flower in the painting.” Her observation about the peonies’ lack of smell proved correct – one illustration among many of her intelligence.

The first contact with astronomy and the study of the stars occurred through her tutor, the Chinese ambassador Lin Fang, who was also an astronomer. At the age of 15 she was introduced to Confucianism, which soon became an obstacle to her thirst for knowledge. The Confucian model, indeed, placed women in a subordinate position within the family, which meant that education in general, let alone astronomy, was not considered suitable. Sonduk, however, used to make observations every night and was mostly self-taught. A clash of wills was inevitable.

One day, Sonduk expressed her wish to talk about astronomy to the Chinese ambassador, but his answer was a cold shower for such a brilliant girl. Convinced of the necessity of a strictly domestic occupation for females, he replied: “Surely you can’t think I can have a conversation on such important topics with a young woman! It would be unnatural and totally inappropriate.”

However, he had soon the chance to ponder the appropriateness of such a conversation when, during a solar eclipse that occurred in Korea, the young princess was able to predict the event and its duration with high accuracy. It was apparent that her knowledge was more than enough to discuss such matters with him on even ground! {%recommended 6780%}

This angered the ambassador even more. He gave her another bit of advice: “Astronomy is not for women,” he said. “Do anything feminine, such as care of silkworms!” Eventually, this influential diplomat from a powerful neighbouring country managed to convince Sonduk’s father to preclude the princess from any further study of the stars.

End of the story? Actually, Sonduk was able to take her revenge when she became ruler of Silla, in 632 CE or, according to other scholars, in 634. We do not know if she managed to remain personally involved in astronomy, but history has passed down to our hands her main contribution to the science: the construction of the astronomical observatory called Cheomseongdae, or the Tower of the Moon and the Stars. 

Still standing today, it is considered the most ancient observatory in the Far East. Sonduk had begged her father for several years to set out on its building, but eventually accomplished the challenge on her own. It has survived mostly intact, and can still be visited in the ruins of the ancient capital of this dynasty, Gyeongju, about 100 kilometres north of Busan, in South Korea. {%recommended 6980%}

The tower was built with 27 circular levels of stone blocks – possibly a reference to the queen herself, the twenty-seventh ruler of Silla – placed in between a square base and a square top. It is more than nine metres tall and still challenges the centuries. Among other uses, it functioned as a calendar that could mark the change of the seasons.

According to the historical accounts, when astronomers were observing in Sonduk’s tower, they laid on their back and watched the celestial objects through four domes on the top, arranged in a square and oriented towards the four cardinal points.

Curiously, the only entrance is a square opening, facing south, about four metres off the ground. It can only be reached by an external ladder. Perhaps the queen wanted to be sure that her astronomers weren’t tempted to finish their shifts early!

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Gabriella Bernardi is a science journalist and author based in Turin, Italy. Her two most recent books are Giovanni Domenico Cassini: A Modern Astronomer in the 17th Century (Springer, 2017), and The Unforgotten Sisters: Female Astronomers and Scientists before Caroline Herschel (Springer, 2016), on which this story is based.