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= Korea's Astronomy = Astronomy first arose in Korea as a supplement to agricultural techniques to predict seasons and weather. Astronomy in the early stages was focused on tracking the motions of the Sun and planets in our solar system. Notable historical innovations were the Cheomseongdae (an ancient astronomical observatory), Cheonsang Yeolcha Bunyajido (astronomical map engraved in stone ), Angbuilgui (a sundial), and Okru (water clock).

Nowadays, South Korea has multiple institutions that take the lead in advancing astronomy research. Korea Astronomy and Space Science Institute (KASI) established on September 13th, 1974 is the central institution for astronomy development funded by the Korean government. 8 universities provide astronomy education above the college level. There are multiple observatories serving the purpose of astronomical research and public outreach.

History of Korean Astronomy
Astronomy was integrated into agricultural purposes as a prediction for farm seasons and weather was essential for cropping. By observing the night sky, astronomers pinpointed the sowing, plowing, and harvesting period accordingly.

Three Kingdoms of Korea (Samhan)
Historical documents indicate records of multiple lunar and solar eclipses. The record of the eclipse first appears in the Samguk Sagi, a historical book written during the Goryeo Dynasty. In Silla, 29 solar eclipses were recorded during 965 years from 54 BC to 911 BC. There are 11 observations in Goguryeo for 445 years and 26 observations in Baekje for 606 years.

In addition to the solar and lunar eclipses, the movement of Mercury, Venus, Mars, Jupiter, and Saturn was considered to be fortune tellers. These planets were thought to signify important events in the country such as an invasion, the death of the king, the birth of a prince, and more. Due to such reason, astronomical events are often described in Korean traditional stories and legends.

Comets have also been observed 32 times in Silla, 10 times in Goguryeo, and 15 times in Baekje, considered an important astronomical phenomenon.

Silla's Cheomseongdae is well known as one of the oldest observatories in the world. Cheomseongdae was built in 647 in the 16th year of Queen Seondeok, with a height of 9.1m, with a diameter of 4.9m.

The Sundial clock or water clock are other historical artifacts that represent Korean astronomy. These were used to interpret the season of the year or measure rainfall.

Goryeo Dynasty
During the Goryeo Dynasty, there was an observatory called Cheomseongdae, which was located on the west side of Manwoldae in Kaesong. The government of the Goryeo dynasty picked officials to be in charge of astronomy, history, and time from the beginning. However, astronomy did not develop further because of around 30 years of war with Mongolia. In 1281, the Yuan Dynasty of China introduced the Chinese calendar to reorganize astronomical observation facilities, and in 1308, Seoungwan, a specialized government office, was established. During the Goryeo Dynasty, records show 20 observations of a potential supernova and 67 observations of the comet.

Joseon Dynasty
Astronomy made significant progress in the early Joseon period when the dynasty was politically stable and agricultural productivity was the highest. Taejo, the very first emperor of the Joseon Dynasty, wanted to produce a new astronomical chart to emphasize that Joseon was "the new dynasty established by the will of heaven" after he ascended the throne. After years of work, 11 scholars, including Kwon Geun and Yoo Young Taek, created a stone-carved astronomical chart called the "Cheonsang Yeolcha Bunyajido."

Additionally, King Sejong made his calendar at Seoungwan, an astronomical government office. To this end, the construction of astronomical instruments was carried out most actively from 1432 to 1438. At that time, Lee Soon-ji and Kim Dam worked for the office. Meanwhile, Icheon and Jang Yeong-sil were mainly in charge of producing astronomical instruments.

In 1433, Ganuidae, an observatory, was established inside Gyeongbokgung Palace, where various observation instruments were installed, including Ganui and Honcheonui, which observe the stars, Angbuilgui, a sundial, and Kyugilu and Okru, a water clock. Astronomy during the Joseon Dynasty in the 15th century reached a world-class level.

However, two Japanese invasions since the 16th century have burned most astronomical observation instruments, consequently stopping the development of astronomy.

Entering the 18th century, "Honcheonjeon," an astronomical chart produced under the influence of Western astronomy, recorded the distance from Earth and the period of revolution of the solar moon, Saturn, Jupiter, Mars, and Venus observed with a telescope. From 1910 to 1945, during the Japanese occupation period, Korean astronomy was not able to progress.

Astronomy Education
Based on 2018, Korea has 8 universities that provide a major degree in astronomy. The institutions are the University of Science and Technology (UST), Kungpook National University, Kyunghee University, Seoul National University, Sejong University, Yonsei University, Chungnam National University, and Chungbook National University. Among the 8 universities, UST only provides a graduate program for astronomy, which means that there are only 7 institutions that you can attend if you were to major in astronomy. The typical courses that are required for an astronomy major are math and physics. Typically, Introduction to Physics, Introduction to Astronomy, Calculus, Differential Equations, and Linear Algebra are representative basic level classes that are required for the astronomy major. The middle-level astronomy courses require Classical Mechanics, Electrodynamics, Astrodynamics, Modern Physics, Observational Astronomy, and Analytical Physics. Upper-level courses include Space Environment, Astronomical instruments, Radio astronomy, Astronomical image processing, galactic astronomy, and cosmology.

Korea Astronomy and Space Science Institute (KASI)
Korea Astronomy and Space Science Institute (KASI) was established on September 13th, 1974, which aims to conduct a comprehensive study of astronomy and space science, manage the operation of large observation facilities and development of equipment, perform national astronomical services, enhance astronomical knowledge to the public, and to promote cooperation in astronomy research with the Korean government, private sectors, corporations, and organizations.

There are many ongoing research in astronomy through KASI: Galactic Evolution Group is one of their famous representative research groups.

KASI Galatic Evolution Group
The Galactic Evolution Group is using various observation facilities, cosmological simulations, numerical experiments, and artificial intelligence to study how galaxies were initially formed and evolved in space. The group utilizes two approaches to study galaxies: conducting optical observations or producing simulations. The research is conducting a wide range of studies, from nearby galaxies to primordial galaxies at the end of the universe, using a variety of techniques, including the development of wide-field telescopes specialized for exploring very dark galaxies, special spectrometers capable of measuring spectra simultaneously, and three-dimensional spectrometers with high efficiency. Additionally, the Galactic Evolution Group uses a supercomputer to simulate the formation and evolution of galaxies from the beginning of the universe. In the past, observations were only available to a small number of astronomers, but in recent years, massive data have been released to the public. Thus, the group focuses on introducing astronomical big data analysis techniques and Machine Learning to automate the process of data analysis. Major ongoing projects are working with LSST data, K-DRIFT (KASI Deep Rolling Imaging Fast-optics Telescope), K-SPEC (KASI SPECtroscopic survey), 3D analysis of spectroscopic data, cosmological simulation studies, and SPHEREx space telescope research. The group also collaborates with KMTNet, ALMA, JCMT, and JVLA.

Observatories
The purpose of observatories can be mainly divided into two categories: educational purpose and research. Observatories that solely have educational purposes are often located in the science centers along with the planetariums. These observatories are not necessarily located in the best place for observing since museums are likely located within cities where light pollution is present. Major astronomical research institutes are all managed by the Korea Astronomy and Space Science Institute, funded by the Korean government.

Soebaksan Observatory
Seobaksan Observatory located in Sobaeksan National Park (639, Sobaeksan-gil, Danyang-eup, Danyang-gun, Chungcheongbuk-do, Republic of Korea). It is a national facility managed by the Korea Astronomy and Space Science Institute (KASI). In 1972, the national observatory construction committee decided to establish the observatory, and thus the observatory's telescope was built in November 1974. The very first observational research done after its establishment was observing the Orion Nebula.

The observatory is involved with various research topics, which can be divided into mainly 7 categories of the following research topics.

1) Measuring physical quantities (mass, temperature, more) of transiting binary systems and variable stars via lightcurve analysis

2) Exoplanet detection through variable star timing analysis

3) Transiting exoplanet follow-up observations

4) Near Earth Object (NEO) research such as asteroids

5) Synchronous satellite position observations

6) Variable star research within star clusters

7) Photometry for comets, supernova

The telescope at Soebaksan Observatory is the Boller & Chives 24-inch (61 cm) Reflector.

Bohyunsan Optical Astronomy Observatory
Bohyunsan Optical Astronomy Observatory (BOAO) is built on the top of Bohyeonsan Mountain at an altitude of 1,124m located in San 6-2, Jeonggak-ri, Hwabuk-myeon, Yeongcheon-si, Gyeongsangbuk-do, Republic of Korea. It is one of the three major astronomical observatories in Korea along with Sobaeksan Astronomical Observatory and Taeduk Radio Astronomy Observatory.

BOAO has a 1.8m reflective telescope and solar flare telescope in Korea. Among 13 asteroids found in Korea, 12 were discovered at BOAO. Notably, the name of the 1.8-meter diameter reflective telescope is "Doyag," which also appears on the back of one of the Korean bills. Because it is a facility where astronomers conduct astronomical observations and research, visitor times are sometimes limited. The visitor center at the top of Bohyeonsan Mountain is open to the public for tours.

Separately, Yeongcheon Bohyeon Mountain Astronomy Science Museum, built under the mountain in Yeongcheon-si, is a civic observatory that teaches and observes astronomy for the general public and is located at 681-32 Byeolbit-ro (689 Jeonggak-ri), Hwabuk-myeon, Yeongcheon-si, Gyeongsangbuk-do. The Bohyeonsan Astronomical Science Museum will hold a star observation event for ordinary visitors at night.

The observatory has the following instruments available for research.

1) 1.8m reflector

2) Solar flare telescope

3) Visible light photometric 4K CCD camera

4) Visible light spectroscopy BOES (Bohyunsan Optical Echelle Spectrograph)

5) Infrared photometric instrument KASINICS (KASI Near-Infrared Camera System)