• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.329-332
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• 2005

The purpose of the East Asian Young Astronomers Meeting (EAYAM) is to provide a chance for young astronomers from or working in China, Korea, Japan, and Taiwan to meet, learn about each other's scientific research, exchange ideas and cultural views, and find out more about leading research facilities in the different member regions. I report on the inaugural EAYAM held in Taiwan in 2003, and the future of this meeting. The purpose of the EAMA Schools is to teach young astronomers how to make best use of the research facilities of member regions. The first EAMA school is currently being organized to better inform young astronomers on using the SUBARU telescope.

• Publications of The Korean Astronomical Society
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• v.26 no.4
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• pp.147-157
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• 2011

I found evidence that Kim Y$\breve{o}$ng (金泳, 1749-1817) is the author of the Korean Poch'$\breve{o}$n'ga with New Charts published in 1792 by the Astronomical Bureau of the Chos$\breve{o}$n dynasty. I reconstructed a history of Kim Y$\breve{o}$ng from various literature remained in other persons' anthologies and governmental records. My findings on the author and publication year can help to solve the problem on the origin of star charts in the Poch'$\breve{o}$n'ga with New Charts. I also considered the changes of Chinese Bu-Tian-Ge and their star charts after Chongzhenglishu (崇禎曆書). I found that the new charts in the book of Huantiantushuo published by Li Mingche (李明徹, 1751-1832) in 1819 are approximately the same to those in the Poch'$\breve{o}$n'ga with New Charts by Kim Y$\breve{o}$ng in 1792.

• Journal of Astronomy and Space Sciences
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• v.26 no.3
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• pp.355-374
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• 2009

We analysed the old automatic clock and time signal system that was used by the national astronomical agency in East Asian Area. Jagyeongnu is a kind of water clock that was operated by the flowing water in Joseon Dynasty. Seowoongwan managed the water clock so as to keep the standard time system in the dynasty from the 16th year (1434) of King Sejong's reign. In 1438 the Okru that was invented in the period. Such kind of clock system already was used in China, which was Shui $y\ddot{u}n$ i hsiang t'ai (水運儀象壹) in 1092. During the period Joseon Dynasty, China and Japan had been kept the time system that one day is divided into 12 shin (12辰) or 100 gak (刻). However detailed part of the system had a little difference among the three countries. Though the whole system of water clock in Joseon had manufactured on the basis of Chinese, it had been gradually developed by own method and idea. In this study we show the historical records of the standard time keeping system in East Asian history. And then we can inform materials on the structure and functional devises for the purpose of new restoration models about the automatic clock and time system.

• Journal of The Korean Astronomical Society
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• v.52 no.4
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• pp.99-108
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• 2019

This work addresses the development of the astronomical observatory all through history, from an architectural point of view, as a building in relation to the observing instruments and their functioning as a heterogeneous work center. We focused on 32 observatories (in the period 1259-2007) and carefully analyzed the architectures. Considering the impact of the construction itself or its facilities on the results of the research (thermal or structural stability, poor weather protection, turbulence, etc.), there is little attention paid to theories or studies of the architectural or construction aspects of the observatories. Therefore, this work aims to present a theoretical-critical contribution that, at least, invites the reflection of those involved in the development of astronomical observatories in the future.

• Journal of Space Technology and Applications
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• v.1 no.1
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• pp.104-120
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• 2021

Some optical schemes of lenses for spacecraft developed by the author are considered. The main optical characteristics of telescope lenses of various architectures are compared. We propose compact solutions of mirror, lens-mirror, and lens systems with maximum available angular resolutions and other parameters. Examples of calculating the optical systems of lenses used for various tasks both in the field of astronomy and in the field of remote sensing of the Earth and other planets are given. The example of onboard computer system is discussed. Practical recommendations on the development and use of telescope lenses are given.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.59.2-59.2
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• 2019

In this talk, I will explain the implications of a rapid appearance of dark energy between the redshifts ($z$) of one and two on the expansion rate and growth of perturbations. Using both Gaussian process regression and a parametric model, I show that this is the preferred solution to the current set of low-redshift ($z<3$) distance measurements if $H_0=73~\rm km\,s^{-1}\,Mpc^{-1}$ to within 1\% and the high-redshift expansion history is unchanged from the $\Lambda$CDM inference by the Planck satellite. Dark energy was effectively non-existent around $z=2$, but its density is close to the $\Lambda$CDM model value today, with an equation of state greater than $-1$ at $z<0.5$. If sources of clustering other than matter are negligible, we show that this expansion history leads to slower growth of perturbations at $z<1$, compared to $\Lambda$CDM, that is measurable by upcoming surveys and can alleviate the $\sigma_8$ tension between the Planck CMB temperature and low-redshift probes of the large-scale structure.

• Journal of Astronomy and Space Sciences
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• v.29 no.2
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• pp.175-180
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• 2012

White dwarf stars have played important roles in rather diverse areas of astrophysics. This paper outlines how these stellar remnants, especially those in widely separated "fragile" binaries, have provided unique leverage on difficult astrophysical problems such as the ages of stars, the structure and evolution of the Galaxy, the nature of dark matter and even the discovery of dark energy.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.51.4-51.4
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• 2018

Luminous blue variables (LBVs) are luminous evolved massive stars (thus with very large initial masses) typified by their irregular variabilities, which are sometimes associated with eruptive mass loss. G026.47+0.02 is one of the known Galactic LBV surrounded by large circumstellar shell (r~1') detected in far IR. In this presentation, we report the identification of another shell of smaller radii (r~20") indicating that the central star experienced multiple episodes of eruptions. We present detailed multi-wavelength study of the inner shell in near IR and sub-mm, with which we reconstruct its mass-loss history.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.35.5-36
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• 2021

'역상고성'은 '신법산서'에 수록되어 있는 티코브라헤의 역법체계와 그 밖의 천문 내용들을 중국인 천문학자들에 의하여 확실하게 정리를 하였지만 '역상고성'에 따른 추보는 천상과 불일치를 보게 되었다. 藪內淸(야부우치 키요시) 저(1969), 유경로 역(1985)에 의하면 이러한 불일치는 옹정 8년 6월 초 1일의 일식이었는데 예보의 오류를 정정한다는 것을 중국 천문학자들이 감당하기 어려웠다. 퀘글러(Ignatius Kögler, 戴進賢, 1680~1746)와 페레이라(Andreas Pereira, 서무덕(徐懋德), 1690-1743) 등의 선교사 천문학자들이 칙명을 받아 종사하게 되고, 이들이 중심이 되어 '역상고성'보다 더 진보된 서양천문 역법에 기초를 둔 역서가 편찬되게 되었다. '신법산서'와 '역상고성'은 모델에서는 평원(平圓)을 사용하지만 '역상고성후편'에서는 타원(楕圓) 모델을 사용하게 된다. 건륭 7년(1742년)에 10권이 완성되어 '역상고성후편'이라 명하였다. 타원모델을 채택하였지만 지동설에 대한 내용은 전혀 기술되어 있지 않다. 아마도 태양이나 달의 운동을 추보하는데 지구를 중심으로 해야 하기에 이에 대한 언급을 필요치 않았을 수도 있다. '역상고성후편' 은 태양과 달의 운행, 일식과 월식에 대해서만 다루고 있다.그러나 '역상고성'에서는 청몽기차나 지반경차를 티코브라헤의 표 값을 그대로 사용하였고, 이 값들이 관측과 관련이 되어 있음을 설명하려는 무리를 두고 있다. 너무 정확하게 값들이 관측 값들로부터 유도되어 의심이 갈 정도이다. 카시니(Giovanni Domenico Cassini, 喝西尼, 1625~1712)는 자신의 동료 리셰와 함께 파리와 프랑스령 기아나 카이엔에서 충의 위치에 있는 화성과 부근 별의 고도를 관측하여 충의 위치에 있는 화성의 시차를 측정하여 최초로 태양과 지구 사이의 거리를 어림하고, 태양의 지반 경차를 현재와 값과 거의 비슷하게 얻었다. '역상고성후편'에서는 이 내용을 상세하게 다루고 있다. 또한 대기에서 입사각과 굴절각 사이에 Snell의 법칙이 성립하는데 이를 이용하여 모호하게 알았던 청몽기차를 대기의 굴절을 이용하여 현재의 값과 비슷한 값을 얻어 사용할 수 있게 되었다. 이는 모든 천체의 위치를 관측하는데 있어서 매우 정확한 값들을 얻을 수 있게 되고 이에 따라 황도-적도 경사각도 정확하게 얻어진다. '역상고성후편'은 옹정원년을 역원으로 하고 있다. 태양의 운행에 있어서 케플러의 타원 궤도를 이용하게 된다. '신법산서'와 '역상고성'에서는 평균근점이각 M을 모델에서 보여 줄 수 있지만 타원 궤도에서는 이 각이 면적각으로 주어지고, 원 대신 타원을 다루기에 쉽지 않다. 현재는 케플러 방정식을 풀어 가감차를 구하게 되는데 이를 기하학적으로 풀이하는 차적구적법을 소개하고 있다. 이와 함께 면적을 이용하여 타원계각과 타원차각을 구하는 차각구각법도 소개한다. 타원계각과 타원차각을 모두 고려하였기에 현재의 태양의 운동을 기술하는 타원모델과 완벽하게 같다. 다만 사용하는 상수가 아주 조금 다를 분이다. 태양의 경도를 추보하는 방법도 동지점을 기준으로 하고 현재의 방법과 동일하다. 달의 운행도 타원 궤도를 사용한다. '역상고성후편'의 내용은 우리나라의 전해져서 1860년 남병길이 쓴 '시헌기요(時憲紀要)'에는 태양, 달, 일·월식, 오행성의 운동, 항성의 위치, 시간 등을 추보하는데 필요한 내용들이 매뉴얼화 되어 기록되어 있고, 1862년 남병철이 쓴 '추보속해(推步續解)'에도 같은 내용을 담고 있다.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.118.2-118.2
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• 2014

As the most sensitive radio interferometer ever operated in millimeter/submillimeter, the ALMA has opened a new window on extragalactic astronomy. Its superior resolution and sensitivity allow the community to study the gas kinematics of distant galaxies as well as the molecular gas properties of nearby galaxies in GMC scale, already in its early commissioning stage. Also the ALMA provides a great tool to probe the dust contents of extragalactic sources at all redshifts, which is important in understanding of galaxy formation and evolution history over cosmic time. In this presentation, I will review the ALMA capabilities with the emphasis on the extragalactic science. I will also revisit some highlights from the early science and discuss future perspectives.