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  • Writer's pictureDale DeBakcsy

Queen Seondeok and the Construction of East Asia’s First Astronomical Observatory.

It is one of the great stories in the Korean royal tradition. A young princess named Deokman is brought a painting of peonies by her father, King Jinpyeong, along with some seeds of the flower. She regards the picture and remarks that the flowers are beautiful, but it is a shame that they have no scent. The King has the seeds planted, and when they bloom, the people of the Court are amazed to find that the Princess’s ’prediction had come true, and the flowers possessed no aroma. The King, taken aback, asks her how she knew this would be the case, to which she responds that there are no insects on or around the flowers in the picture, which indicates that the peonies must not have a strong smell.

As with many tales from antiquity, and particularly those pertaining to future monarchs, we can be healthily skeptical about whether these events actually happened, but here it is not so much the factuality of the events that is important, but what we are told about people’s lingering historical perception of Princess Deokman, the future Queen Seondeok (595/610–647), by the story. The reign of Seondeok was one of cultural and intellectual renaissance for the Silla Empire (which lasted nearly a thousand years, from 57 BCE to 935 CE, and which managed the unification of the three main Korean Empires shortly after Seondeok’s reign, in 668), and as such its ruler needed an origin story to speak to her most important traits, as perceived by her time: her keen analytic eye, her forthrightness, and above all, her intelligence.

It was this intelligence that compelled the son-less King Jinpyeong to forgo his plans of elevating his son-in-law to the throne, and to give Deokman her chance to rule as Silla’s 27th monarch, and its first woman ruler. That decision, however, was not met with universal approval, and in 631 a rebellion was planned to stop Deokman’s ascension. That plot was discovered, however, and its leaders executed, paving the way in 632 for Princess Deokman to become Queen Seondeok, and to begin a reign that would last until her death in 647.

While much of her reign was occupied with forming alliances with China (then in its Golden Age under the Tang Dynasty) to fend off the opportunistic attacks from the other two great Korean kingdoms of the era, the Goguryeo and the Baekje, she lingers in the memory of her country less for her military experiences and more for her cultural, scientific, and governance innovations. Her achievements in promoting Buddhism in her country (particularly through the construction of the towering nine-story Hwangnyongsa temple) and developing a government that sought to aid the poor and reduce taxation are accomplishments well worth discussing, but we are here for astronomy today, and so it is to the second year of her reign that we shall turn, when she had erected Cheomseongdae, possibly the oldest dedicated observatory in East Asia, and certainly the oldest one still standing.

Cheomseongdae is built of 365 stones, one for each day of the year, and consists of 27 layers, perhaps to represent Seondeok’s status as Silla’s 27th ruler, with a base of 12 stones, likely referring to the twelve months of the year. The top of the observatory consisted of an area where Korean astronomers could lie down to observe the night sky through one of four domes placed at the four cardinal points of the compass. Seondeok’s reason for constructing it is usually said to have been for the benefit of Korea’s farmers, who needed better astronomical data to plan their harvest cycles, but part of the reason might have been more personal.


When she was young, a Chinese astronomer visited Silla in an attempt to convince King Jinpyeong to adopt the Chinese calendar system. Seondeok, then still Princess Deokman, was eager to speak with this learned man on the subject of the night sky, but he categorically refused to discuss such a topic with a young woman and when, later, she predicted the duration and progression of an eclipse with a startling degree of accuracy, her ability sent him into a rage during which he blurted out, ‘Astronomy is not for women!’ and then proceeded to remonstrate with Jinpyeong to prevent his daughter from learning more astronomy, which advice he apparently heeded, forbidding her to continue her studies of the subject. I would like to think that, in addition to the generally benevolent policy of building Cheomseongdae for the farmers of her kingdom, there was at least a little bit of personal thrill in it, as she saw her observatory rising from the ground and realised that astronomy could in fact be for women, and soon would be.


If you'd like to read more about women astronomers like this one, check out my History of Women in Astronomy and Space Exploration, which you can order from Amazon, or from Pen and Sword US or UK.


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