A BRIEF HISTORY OF THE KOREAN ASTRONOMY

1. Old Choson or Tankun Choson

The first nation that had been ever built by Korean was the Old Choson dynasty. According to the Remained Historical Affairs of the Three Kingdoms  this country was built in B.C. 2333. Old Choson was perished in B.C.108 when it was invaded by the Han dynasty.

Most of the historical records of this period are found in the Handan Old Archives  and the Ancient History of Tankun Choson and Kija  Choson . In these two books, we can find records of ten solar eclipses, one aggregation of five planets, and one big tide.

An attempt to reproduce these astronomical events by numerical simulation was made by La and Park (1993). In spite of the difficulties concerning the uncertainty of the exact dates and the definite location of the captital city of the Tankun Choson, it is concluded that five records out of ten were realized (La and Park 1993).

One can be reminded of the fact that the aggregation of the five planets is a rare event. When they calculated the position of the five planets around B.C.1733, they found that there were really one aggregation of the five planets. The nearest such events before and after this aggregation are spaced by 550 years. In view of this fact that the two archives recorded such a rare event correctly, they draw a tentative conclusion that these archives are at least partially reliable (La and Park 1993).

Old Choson continued to exist throughout the bronze age and the iron age. So there are a large number of archaeological antiquities. For example, near Pyeng-Yang  are some of them, which indicate that there were some kind of astronomical activities in this era.

For more specific, various Eastern asterisms are engraved on the head stone of the about 200 dolmens. These antiquities are thought to be related to the primitive belief that spirits become stars on the heaven.

2. The Era of Powers

After the invasion of the Han dynasty and wide spread of ironware, around the 2nd century B.C., Tankun Choson) was split into dozens of small countries.

Unfortunately there are few first-hand records for this period. However we have several history books written by some foreign historians, where some pieces of records about the ancient Korean countries. For example, according to Sangouji, the Ye, which is one of such ancient Korean countries, is described as follows. "in the Ye  people observe the asterisms to predict whether it will be a good harvest or not". In view of this description we can see the people in this period observed the stars and were very familiar to the astronomy in their life.

3. The Three Kingdoms

By the 5th century A.D., there had been continuing mergers between small countries and finally there appeared four countries : Koguryo , Paikche , Silla , and Kaya . Soon Kaya was conquered to be parted its land by Silla and Paikche. As a matter of fact, it is difficult to find astronomical records or antiquities of Kaya.

As for the other three countries, the history of this period remains mainly in the History of the Three Kingdoms  and also in the Remained Historical Affairs of the Three Kingdoms .

But here let's first look around the vivid frescos painted by people of this era. There are a lot of frescos painted on the inner walls of old tombs of the Koguryo era. Upon seeing these pictures one may get a strong feeling that the Koguryo people had a keen interest in the heavenly bodies and a high level of astronomical knowledge. Asterisms and the abstract symbols that stand for the heavenly bodies or astronomical concepts were painted. Moreover there are frescos that displays legends about asterisms.

According to the inscriptions of Chon-Sang-Yol-Cha-Poon-Ya-Ji-Dowe can infer that its prototypical map was originated from the Koguryo era. In view of the painted asterisms, it may naturally feel that their achievements in astronomy were enough to make such a prototypical map.

In case of Paikche, in A.D. 602, Kwan-Nuk, scholar of Paikche, went to Japan to hand over books on the calendar, astronomy and geomancy. Because nearly all of their cultural achievements were destroyed by invaders (Silla and Tang), we can't find enough historical or archaeological materials to testify the level of Paikche's astronomy. However reproducing their astronomical records, we can imagine the astronomical achievements of Paikche people.

According to one of the record, Venus appeared in daytime at A.D. 224, which is reproduced as a real event. An observation of a delicate phenomenon such as this provides a hint indicating that they possessed a profound knowledge about motion of heavenly bodies.

 As for Silla, we have several antiquities, which shows that astronomical activities were comparably high with the two preceding kingdoms. In A.D. 647 reigned by Queen Sunduck , the astronomical observatory Chumsungdai , the oldest observatory remaining in Korea, was constructed.

In the two books mentioned above, we can find the valuable astronomical records which the passionate and skillful people of the Three Kingdoms left to us.

The records include the occultations of the planets by the Moon, the aggregations of several major planets, the appearances of Venus in the day-time, guest-stars or novae , and the solar and the lunar eclipses.

 Park and La (1994) performed nemerical calculations to check the reliability of the astronomical records of the early Three Kingdoms. They conclude that most of the records can be reproduced. Especially the results on the eclipses show that there are separate locations of strong concentrations in the mean magnitude of solar eclipses. Assuming that these locations indicate those of the optimal observing sites, it is very interesting to note that they coincide with those of the capitals of each kingdom.

They also performed Monte Carlo simulations to show that the records on eclipses can not be what were randomly copied from Chinese history books. These results show that the people of the Three Kingdoms observed the astronomical phenomena independently.

Historically there are still some controversies on this result on the location of each countries. Personally I think that an analysis of occultation records will resolve some controversies on this topic, because occultations are very rarely occurring phenomena and can be observed from a very locallized and narrow region on the earth.

4. Palhai and the latter period of Silla

Today it is a very difficult matter to find the antiquities or the first-hand archives of the Palhai era, let alone the second-hand astronomical records.

In view of the generally-agreed fact that Palhai inherited the culture of the Koguryo, the Palhai people must have performed a variety of astronomical activities.

In the 7th century, the latter period of Silla begun. Since then the interaction between the Tang dynasty and the Silla dynasty had increased. In 682 a monk from Tang, Toh-Cheung, presented a celestial planisphere to Silla.

In 718 the first clepsydra was constructed. In 749 a doctor of astronomy  and three doctors of clepsydra were appointed.

There is a record which indicates the fact that the Silla people could calculate and predict solar eclipses. According to this record, "in A.D. 800 there should be a solar eclipse, which, however, did not occur". We may draw a tentative conclusion that their calculations were not precise enough.

There are only two pieces of records that are believed to be the lunar eclipses, and they are successfully reproduced to be the penumbral eclipses. However it does not seem that the Silla people observed the lunar eclipse intentionally. We do not know whether this fact is related to the political reasons or the technical reasons.

5 Koryo(918~1392)

Astronomical archives of this period include the History of Koryo , the Brief History of Koryo. And these records are summarized in the Choson era into "the Review on the Old Astronomical Records of the Koryo Dynasty" .

According to the History of Koryo, the most remarkable observational astronomer was Oh Yoon-Boo. He was such a passionate observer that he would not sleep in order to observe the heavenly bodies. Eventually he made a whole sky star atlas and became famous in the Eastern Asia of the Yuan dynasty. Unfortunately this atlas is lost.

There remains an old observational station at Kaisung (°³¼º), the capital city of Koryo. Also there was an royal observatory called Seo-Woon-Kwan (¼­¿î°ü) : an institute for the observations of astronomical and meteological phenomena.

In this period the Arabic astronomy was introduced to Koryo. One of the vivid examples is the Zodiac animals engraved on the bronze mirror. In general it is certain that these figures were originated from the Arab.

Generally speaking the Arabic astronomy was flown into the Eastern countries with the aid of Buddhism. After the Arab was included into the territory of the Mongol Empire, the Arabic astronomical knowledge was begun to be directly imported to Koryo.

For example, in the Yuan dynasty, Shou-Shih-Li, a method of making an astronomical calendar, was developed by one of the most famous Chinese astronomers Kwok  inspired partly by the Arabic astronomy. Soon Shou-Shih-Li was transferred to Koryo by the Mongol empire to be written in the History of Koryo.

In this way the Arabic Zodiac came to appear on the bronze mirrors of the Koryo period. Related with this we note that in Chon-Sang-Yol-Cha-Poon-Ya-Ji-Do the names of Zodiac are seen.

In contrast to the fact that the Ming dynaty destroyed nearly all the astronomical achievements of the Mogol empire, the Koryo dynasty preserved and handed them over to the Choson dynasty, where further significant improvements were made.

Astronomical records of this era are as follows : solar and lunar eclipses, aurorae, occultations of stars by the Moon, occultations of stars by the planets, occultations of planets by the Moon, sunspots, comets, novae or supernovae, and various and numerous meteological phenomena.

Especially an analysis of the sunspot records indicates that those records have a trend showing the well-known 11 year long-term period and, what is more, about 100 year period .

As for solar eclipses, among total 132 records 109 are reproduced as real. There are records that were calculated and predicted but not able to be observed because of the bad weather. We can infer from these facts that Koryo people could calculate the solar eclipses as is the case for the Silla people (Park and La 1994).

As for the lunar eclipses, it is concluded that the Koryo people observed mainly the umbral eclipses. Among 222 records only a few can not be reproduced and moreover it is because these are due to mere typographical errors in history books or the uncertainty of exact year of records. What is more remarkable is that there are 23 calculated records of lunar eclipses all of which are reproduced as real phenomena. There are such records as "there should be a lunar eclipse but couldn't observe because of rain or thick clouds". Moreover there is a record that "there should be a lunar eclipse but was not(A.D.1030)", which is reproduced to occur in the morning after the sunrise. These facts indicate that the Koryo people had the ability to calculate and predict lunar eclipses even though their computation was not perfect (Ahn 1997).

We have still a lot of topics to study harder, which may help to unveil the hidden astronomical history of the Koryo dynasty

On top of the stony coffin of Kwon Jun , 28 Shu was painted, which are the Eastern asterisms lying on the ecliptic region. These 28 Shu are lunar mensions approximately corresponding to the Western Zodiac constellations. It might not be a mere accidental fact that Kwon Jun is the grandfather of Kwon Keun who played a leading role in the production of Chon-Sang-Yol-Cha-Poon-Ya-Ji-Do. In these respects the Choson people inherited their astronomical knowledge and interests on the heaven from the Koryo dynasty.

6. Choson

We can see the historical records of this period mainly in the Real Records of Choson Dynasty and the Diary of Royal Secretary  and so on. For more than 500 years, they had piled up the valuable and detailed astronomical records. For example, the Kepler supernova, SN1604, was monitored and reported daily except possibly for rainy or cloudy days.

However, in spite of its high value as astronomical data, the astronomical records are not even sorted into to each phenomenon. It is, I think, our task to study these records scientifically .

a. the First Period

In 1396, Chon-Sang-Yol-Cha-Poon-Ya-Ji-Do was engraved on the big and plain stone. It is a celestial planisphere sectioned with Cha  and Poon-Ya. Its map projection law is found to be the polar equatorial and equidistance projection : the linear distance of an object on the map from the center is linearly proportional to the north polar angular distance. A statistical analysis shows us that the circumpolar stars whose declinations are larger than 50 are at the epoch of about 1300. On the other hand the upper culmination stars whose declinations are lower than 50 are at the epoch of the first century.

As is inferred from the inscription on the map, its prototypical map could be made at the Koguryo era. So we can easily understand the prototypical map of the Koguryo era was revised at 1396 when the map was engraved (Park \& Ahn 1996).

It is a very notable fact that this planisphere had been a standard one of the Choson dynasty until the new Western planispheres were introduced to become standard ones. It had profound influences on the Japanese astronomy.

In the 15th century King Sejong promoted science and technology as an efficient way to realize the political idealogy, which was also a tradition of old Chinese politics.

In this period the famous astronomer Yi Soon-Jee played an important role in the field of astronomy. In 1442, he and his collaborators, including Kim Dam, made Chil-Jong-San  which is composed of both traditional and Arabic methods. We may regard Chil-Jong-San as a program to calculate the positions of five major planets as well as the solar and the lunar eclipses. As a consequence, using this method they could make an accurate astronomical calendar. Chil-Jong means the seven luminaries : the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn.

One of the famous technocrats in this period is Jang Young-sil. He made an automated clepsydra named Ja-Kyog-Roo and various astronomical instruments. At the time there were only a few countries who could make such a precise chlepsydra in the world.

The astronomical activities in this period were led by the government. They operated a royal observatory, Kwan-Sang-Kam  and several observational stations. Over two hundred scholars were engaged in this institute. Whenever special celestial phenomena had happened, they quickly observed and reported the result to King and bureaucrats by official documents, Sung-Pyun-Cheuk-Hoo-Tan-Ja, meaning "rapid reports on the observations of celestial events." (Yu 1994)

b. the Middle Period

After the Japanese invasion of Korea in 1592 and the Manchu war of 1636, most of the Korean astronomical achievements were destroyed. In the mean time, the new knowledge of the European astronomy started to appear in Choson, which had been exported to China by the Jesuit missionaries.

In 1631, Jeong Doo-Won brought a telescope from China for the first time in the Korean history. Since then several other people also brought telescopes to Choson. However, it is still uncertain whether or not they used these telescopes to observe the heavenly bodies.

In the 18th century the Korean Renaissance of culture was set in. The scholars who made a practical approach to the nature and the society came to have interests in the European science and technology, especially in astronomy.

One of them is Hong Dae-Yong  who visited Beijing several times and contacted European missionaries to gain access to study European astronomy. In his books he mentioned the rotation of the earth, the infinite Universe, the existence of E.T., and the Galilean relativity in 1760s. Although a large part of the knowledge was borrowed from the Western astronomy, some of his ideas were creative ones. He even made a private observational station in his own house.

A large number of Official astronomers also played a very important role in this period. One of them was an observational astronomer Ahn Guk-Bin who lived in the 18th century. He made a new planisphere which reflected the changes influenced by European astronomy.

c. the Latter Period

In the 19th century, the Choson dynasty began to decline but the astronomical tradition continued.

Nam Pyong-Gil (1820-1869) and his co-workers made Song-Kyong which is a star catalog with star atlas. The catalog lists positions and magnitudes of traditional 1319 stars with their Eastern names and additional 130 stars near the south celestial pole with their Western names.

Ahn et. al. (1996) identified these stars with the stars in the Yale Bright Star Catalog (1996). They conclude that Song-Kyong contains an observational error of a few arc-minute, and that this error is a real observational error. They also found that its magnitude system is very close to the modern stellar magnitude system of Pogson's law.

Furthermore, Choi Han-Ki (1803-1877) referred to Hershell's theory on the structure of the Galaxy, Kant-Laplace theory on the Galaxy formation in his book, "Dynamic Changes of Stellar Chi " published in 1867. He also explained in his book, "the interactions between the Spirit and the Creative Energy ", the refraction of stellar light incident on the atmosphere and the heliocentric motion of the solar system. It is not an exaggeration to say that Choi Han-Ki might make a new paradigm to define the modern science.

When Jung Young-Taik translated and published the history of the Western astronomy in 1908, the Koreans began to get into contact with the modern astronomy for the first time.

Unfortunately, in 1910, Choson was pillaged by the Japanese Imperialism. At the same time, independent developement in astronomy as well as other cultural parts was highly suppressed.

7. Depressed period (1910-1945)

The first Korean modern astronomer is Dr. Lee Won-Chul. He studied in the Yonhee college. When he was a senior he had the first chance to contact the modern astronomy. After graduating from the Yonhee college he went to the United States of America to study astronomy. He investigated the pulsating stars. In 1925 he presented the preliminary results at the American Astronomical Society Meeting. After he obtained his Ph.D. degree in 1926, he came back to Korea to become a prefessor of astronomy in the Yonhee college. Unfortunately under the severe political suppression by the Japanese government-general he had to give up the teaching position.

After the restoration of Korean independence he worked hard to establish the root of Korean astronomy. He died in 1963. Still some people call "$\eta$ Aql" as "Won-Chul's star" to honor him.

8. Modern times

In 1958 the Department of Astronomy at the Seoul National University was established.

On the vernal Equinox in 1965, the Korean Astronomical Society (KAS) was established.

In 1973 the KAS joined the IAU as a regular member.

In 1974 the Korean Astronomy Observatory was established.

In 1978 the Mt. Sobaek Observational Station was constructed. Click to Mt. Sobaek Observational Station Home page

In 1985 the Taeduk Radio Astronomy Observatory (TRAO) was constructed.

In 1996 the Mt. Bohyunsan Optical Astronomy Observatory (BOAO) was constructed.

Acknowledgements

My deepest thank goes to Dr. Lee Hee-Won for his valuable comments and suggestions on the logical context of this work, as well as English. I also thank Dr. Lee Eun-Hee for her sending me the table for matching a lunar calendar and the solar calendar and her Ph.D. thesis on Chil-Jong-San. I am grateful to Mr. Yang Hong-Jin, who provided me with the table on the old Eastern solar eclipses. It is my pleasure to thank Mr. Pyo Tae-Soo now in the Tokyo University for the old paper on the identification of Eastern asterisms in the History of Koryo. I would like to thank Ms. Rita Kim now in the Princeton University for the paper on the Kepler supernova.

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