• 천문학회지
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• 제36권spc1호
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• pp.155-161
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• 2003

In this article I review the past and current status of solar astronomy in Korea and present some future prospects. Along with a brief historical account on the introduction of modern astronomy to Korea, I describe in detail how solar astronomy in Korea has developed since its birth about 20 years ago. With education of solar astronomers at domestic universities and collaboration with foreign scientists in China, Japan and the U. S., there has been a rapid growth of solar physics in Korea in the past decade. For further advance of solar astronomy in Korea, Korean solar astronomers have to build their own observing facilities and develop instrumentation programs. Also it is very important to bring up manpower competent for these projects.

• 천문학회지
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• 제33권3호
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• pp.177-183
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• 2000

We arrange Korean ancient calendar with Solar calendar during Choseon Dynasty(A.D. 1392-1910). In this period, we have one representable history books and several books, and most of information for date are found from them, ChoseonWangjosillok(조선왕조실록) and Jeungbomunheonbigo(증보문헌비고), etc. In those books many astronomical data and calendar information data are contained, so we can make chronological tables. Most of the data are arranged based on those several books, and for doubtable data are identified from eclipse, historical events and lunar phase calculations etc. We find that arranged chronological tables during Choseon Dynasty are similar to that of China and somewhat different from that of Japan. In addition we summarize all misrecorded date data in ChoseonWangjosillok

• Journal of Astronomy and Space Sciences
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• 제21권4호
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• pp.493-504
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• 2004

동아시아의 역사서에는 일식에 대한 기록들이 다른 천문현상들에 비해 많이 나타난다. 이것은 전통적으로 일식은 왕조의 운명과 연관되어있다는 정치적인 사상 때문이다. 조선시대까지도 태양은 임금을 상징하였고, 일식이 일어나면 일식이 무사히 지나가도록 임금이 제사하는 구식례(求食禮)을 지내곤 했다. 따라서 당시의 임금은 일식에 대한 정확한 예보를 얻는 것이 상당히 중요한 일이었다. 그러나 그럼에도 불구하고 조선 초기의 일식 예측은 잘 맞지가 않았다. 이에 세종은 당시 수도인 한양의 위치에 맞는 역법서(曆法書)인 칠정산내편과 칠정산외편을 편찬하였고, 이로 인해 비로소 조선의 자주적인 역법(曆法)이 확립되었다. 칠정산외편은 아라비아의 역법인 회회력(回回曆)을 기초로 해서 만들어진 역법으로 조선 초기의 일식 계산에서는 당시의 여러 역법 계산 결과보다 더 정확하였고, 현대적인 계산 방법과 비교하여 보아도 오차의 범위내에 잘 들어맞음을 알 수 있었다.

• 천문학회지
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• 제53권6호
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• pp.125-138
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• 2020

We determine the observing sites for eclipses of large magnitude recorded in ancient Chinese chronicles from 200 BCE to 900 CE, by adopting the difference between terrestrial time and universal time, ΔT, given by Morrison & Stephenson (2004). The records of solar eclipses with large magnitude are divided into four groups in accordance with the historical variations of the capital cities of ancient Chinese dynasties. We determine areas in which all the eclipses in each group, with an eclipse magnitude larger than a certain threshold value, could be observed. We find that these areas coincide with the historical capitals, which agrees with the general idea that the solar eclipses were observed at the capital of each dynasty. This result also verifies the ΔT values during the period from 100 BCE to 400 CE, during which historical records of eclipses are so rare that the ΔT values can only be obtained by interpolating the long-term data. Moreover, we show that the eclipses described by the term Ji in East-Asian history are not all total eclipses; their mean magnitude is 0.96 ± 0.04. We find that complementary expressions, such as dark daytime and appearance of stars during the eclipse, strengthen the possibility that eclipses described by the term Ji were total. We also provide quantitative definitions for expressions such as 'being not complete and like a hook', 'being almost complete', 'visibility of stars during the eclipse', and 'darkness during an eclipse.' The literal meanings of these expressions are in agreement with the recent physical modeling of sky brightness during total eclipses provided by Können & Hinz (2008).

• 천문학논총
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• 제14권2호
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• pp.129-137
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• 1999

We arranged ancient Korean calendar during Koryo dynasty (A.D. 918-1392) according to Julian calendar. We used two representative history books, Koryo-sa (高麗史) and Koryo-sa Jeolyo (高麗史節要), which contain thea stronomical and the historical records chronologically. We found all 19,727 ganji dates(日辰) and 102 misrecoreded ganji dates in two books. Most of the data are arranged based on those two books, and doubtful data are identified using the eclipse, historical events and lunar phase calculations etc. Although Korea, China, and Japan were using basically the same calendar since ancient times, their calendars show some significant disagreement. We found that arranged chronological tables during Koryo dynasty were, in some cases, different from those of China and Japan.

• 천문학회보
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• 제40권2호
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• pp.39.1-39.1
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• 2015

Korea has a long history in astronomy, which is proved by many observational records written in Korean chronicles. There are 43 sunspot records in Goryeo dynasty (高麗 918-1392) and 13 records in Joseon dynasty (朝鮮 1392-1910). According to analysis of Korean historical records, it is known that sunspot records in Goryeo dynasty show well in match with the well-known solar activity of 11.3 years. It means that Korean historical sunspot records show real solar phenomena. Korean sunspot records also show that solar activity decrease in Joseon dynasty compared with the previous ~500 years. In order to know the change of solar activity in detail, we examine Korean historical atmospheric records which can indicate climate change. We first analyze historical frost records. Korean chronicles have around 600 frost records during the last millennium. We find that the climate change shows sign of cooling down when check the variation of epoch that the first and last frost events in each year are written. This result is well in accord with that of historical sunspot records. Therefore, we claim that solar activity decrease during the last thousand years.

• Journal of Astronomy and Space Sciences
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• 제34권1호
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• pp.55-65
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• 2017

We studied the hour-lines of six extant Yangcheon-cheoks in Korea. To find whether Yangcheon-cheok was used in the whole area of Korea, we calculated the length of shadows of Yangcheon-cheok on the Korean Peninsula, Nanjing and Beijing as well as Hanyang (Seoul), according to 24 solar terms. Comparing the length of shadows with hour-lines of those relics, we could find that Yangcheon-cheok was suitable for use at limited times (from 9:00 to 15:00) during the year. Also, this sundial is more appropriate for use at low latitudes than high ones. Among existing relics, that of Seoul Museum of History made with porcelain was much more suitable to use at Hanyang and its higher latitude. Lee's collection was also suitable to use at Nanjing. It is certain that Yangcheon-cheok was a portable sundial which could be used from nine to fifteen of clock all the year around except for the winter season.

• 천문학논총
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• 제33권1호
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• pp.1-7
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• 2018

In order to encourage collaboration with North Korea in astronomy research field, we have studied the astronomical almanacs published in South and North Korea. The almanac contains fundamental astronomical data including not only daily calendar data but also unique characteristics selected by necessity in each country. We compared the South and North Korean astronomical almanacs in terms of contents, detailed descriptions, unique items, and so forth. We used the 2017 almanac for South Korea and 1993 almanac which is useful for this research for North Korea. We found that there were several differences between South and North Korean almanacs. The North Korean almanac is published for the astronomer or navigator, thus it has supplementary information about spherical astronomy such as precession of the north pole and position of celestial bodies. Whereas the South Korean almanac is published for the general public, and it distinctively contains luni-solar calendar, 24 solar terms, national holidays, etc. This study could be helpful for research cooperation between South and North Korea in astronomy.

• 천문학회보
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• 제40권2호
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• pp.33.1-33.1
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• 2015

M85 is a nearby merger remnant galaxy located at the northern part of the Virgo Cluster. Because of its remarkable merging features, it is an interesting object to investigate its formation history. Globular clusters are a great tracer of the formation history of early-type galaxies, so that we study the globular cluster system of M85. It has been already found that there are "intermediate-color" globular clusters as well as blue and red ones based on the photometric survey using CFHT/Megacam. For follow-up research, we obtain the spectra of 21 globular clusters in the central region of M85 using Gemini-N/GMOS. We estimate their ages and metallicities based on the strength of Lick indices. We detect the intermediate-age population (~ 2 Gyr) with solar metallicities, comprising about 50% of the observed globular clusters, as well as old and metal-poor population. It suggests that M85 experienced a major merging event around 2 Gyr ago. We discuss these results regarding to the formation history of M85.

• 천문학회보
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• 제38권2호
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• pp.93.1-93.1
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• 2013

The Earth's radiation belts consist of an inner belt and an outer belt, being separated by the slot region. It is well known that the variations of the inner edge of the outer belt and the location of the plasmapause (Lpp) are closely related to each other. Different waves exist inside and outside the plasmasphere, playing different roles in the particle dynamics. The plasmapause is well known to be influenced by solar wind conditions and geomagnetic disturbances. Therefore, it is important to precisely determine the location of the plasmapause and develop a prediction scheme. In this study, we identified the location of the plasmapause using the plasma density data from the Time History of Events and Macroscale Interactions During Substorms (THEMIS). The plasmapause is determined by requiring density gradient of a factor of 15 within L-change = 0.5. We statistically determined Lpp as a function of preceding geomagnetic indices. Also, we determined the relations between Lpp and preceding solar wind conditions by estimating correlation coefficients. These relations give us predicting models of Lpp as a function of preceding solar wind parameters and geomagnetic indices. As our database covers a period over the ascending phase from near-sunspot minimum, our statistical results differ somewhat from previous works that cover near-sunspot maximum. Finally, we give some comparative examples obtained from the Van Allen Probes data.