• Journal of Astronomy and Space Sciences
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• 제29권2호
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• pp.209-220
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• 2012

This paper will introduce and overview in general the $Seongbyeon$ $Deungrok$ issued by the Gwansang-gam, the Astronomical Board in the Joseon Dynasty of Korea. All the Chinese characters in the 1668 $Seongbyeon$ $Deungrok$ was deciphered at first and these were translated into Korean and English. With these translations and the word 'white vapor' in particular we discuss the nature of the main object in this $Deungrok$. Lastly, names of observers who engaged in the observations of this 1668 celestial, which are made as a by-product of this research, are introduced.

• 천문학회보
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• 제44권1호
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• pp.63.1-63.1
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• 2019

Solar system small bodies are unusual objects in astronomical survey data in that they are moving on the celestial sphere. In addition, even in a normal status, their magnitudes are changing over time, firstly because their relative positions with respect to the Sun and Earth are continually changing, secondly because they are rotating bodies with non-spherical shapes. Furthermore, some of them might exhibit unexpected activities, which could be caused by mass ejection or disintegration. Detections and observations of such activities are challenging due to their abrupt nature. Therefore, continuous monitoring observations of large number of Solar system small bodies are required to systematically obtain detailed/transient information about them. Since 2018/2019 winter, we have launched a new project using Korea Microlensing Telescope Network (KMTNet) for detecting such transient phenomena of Solar system objects. Our main goal is to monitor the magnitudes and detect sudden brightness changes. We also plan to discover interesting new objects, and monitor rotational brightness oscillations of asteroids. We intend to monitor the magnitudes of ~ 20,000 known Solar system small bodies per night, and acquire lightcurves of ~ 1,000 asteroids.

• 천문학회보
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• 제44권2호
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• pp.44.2-44.2
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• 2019

Comets, one of the least-altered leftovers from the nascent solar system, have probably preserved the primitive structure inside, whereas their surfaces become modified from the initial states after repetitive orbital revolutions around the Sun. Resurfacing makes the surface drier and more consolidated than the bulk nuclei, creating inert refractory dust layer ("dust mantle"). Near-infrared (NIR; 1.25-2.25 m) polarimetry is theoretically expected to maximize contrast of the porosity between inner fresh and evolved dust particles, by harboring more dust constituents in the single wavelength than the optical; thus, intensifies electromagnetic interaction in dust aggregates. Despite such an advantage, only a few studies have been made in this approach mainly due to the limited accessibility of available facilities. Herein, we present our new multi-band NIR polarimetric study of near-Earth object 252P/LINEAR over 12 days near perihelion, together with the results of optical (0.48-0.80m) imaging observations and backward dynamical simulation of the comet. Based on the results, we will characterize the dust properties of the comet and discuss the possible environmental (temperature and UV radiation) effects that could produce the observed phenomena.

• 대한한의학원전학회지
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• 제20권1호
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• pp.113-123
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• 2007

The astronomical understanding of the heavens in "Hwangje-Naegyeong" can be divided into three main fields: the theory of cosmos, astronomy and calender. "Hwangie-Naegyeong" comprised the theory of cosmos, astronomy and calender established in the Han period. Astronomy was to describe the heavenly world and to interpret its phenomena. Calendar was to make numerical representations of the observations of all kinds of celestial bodies and to give them number-mystical meanings. Theory of cosmos treated what ancient Chinese speculated on the structure of the heavens including the earth. These three fields developed independently. However, they can also be be combined into one tradition, the astronomical knowledge. In the Han period that the astronomical knowledge grew from the mere accumulation of primitive knowledge to the established form. Throughout the Chinese history, the essential contents of astronomical knowledge including the theory of calendar, did not change much from what they were in Han period. "Hwangje-Naegyeong" use the lunisolar calendar(太陰太陽曆) and the Calendar in the late Han period(後漢四分曆). The use of the subdivisions of the seasons(24節氣) and the leap month(閏月) in "Hwangje-Naegyeong" means that it adopted the lunisolar calendar. Also "Hwangje-Naegyeong" adopted the Calendar in the late Han period by the four points: "Hwangje-Naegveong" ruled the circulation of the universe(周天度數) at 365, 1/4 terms, use the The Twenty Eight Constellations in astronomical observation, view the heavenly body by the ecliptic(黃道) and mark down year by the Heavenly Streams & Earthly Branches(干支紀年), The 24 solar terms is made by amount of Yang-Gi(陽氣) and samyum and samyang(三陰三陽) represent the amount of Yang-Gi in the earth.

• 대한지구과학교육학회지
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• 제4권1호
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• pp.32-42
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• 2011

The purpose of this study is to provide meaningful basic materials for organizing a science curriculum in future by analyzing the status and changes of contents about astronomical phenomena in textbooks according to the changes of the science curriculum of elementary school. A main target of analysis is science textbooks of elementary school in curriculums from 1st to 7th. For the analysis, the analytic frame based on contents in astronomy textbooks of teachers colleges and colleges of education was used. The result of the analysis is as in the following. First, astronomy accounted for average about 7% of all pages of textbooks in all of science curriculums. The 1st educational curriculum had the most learning quantity of 10.40%, and the 6th curriculum had the least quantity of 4.39%. These results show that astronomy was not a small part and was considered important in each science curriculum of elementary school considering that earth science accounted for 17-26% of all pages in elementary school science curriculum. Second, the things that have been dealt with in common in all science curriculums from 1st to 7th of elementary school are the shape of the earth, the rotation and the revolution of the earth, the occurrence of the seasons, the apparent motion of the sun, the status and motion of the moon, the movement of a star, the brightness and distance of a star, constellations, the sun, planets and others. These contents are expected to be dealt with continuously as basic contents to organize astronomy regardless of the changes of curriculum. Third, in science curriculum of elementary school, astronomical phenomena based on life experiences regarding the earth, the moon and the sun are mainly dealt with in the first and the second grade. Contents requiring principles-understanding and research are dealt with in the fifth and sixth grade. These results show that elementary school science curriculum dealing with astronomy reflects the developmental stages of students and considers principle of learning possibility.

• 천문학회보
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• 제37권2호
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• pp.101.2-101.2
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• 2012

Shocks are ubiquitous in astrophysical plasmas: bow shocks are formed by the interaction of solar wind with planetary magnetic fields, and supernova explosions and jets produce shocks in interstellar and intergalactic spaces. The global morphologies of these shocks are usually described by a set of magnetohydrodynamic (MHD) equations which tacitly assumes local thermal equilibrium, and the resulting Rankine-Hugoniot shock jump conditions are applied to obtain the relationship between the upstream and downstream physical quantities. While thermal equilibrium can be achieved easily in collisional fluids, it is generally believed that collisions are infrequent in astrophysical settings. In fact, shock widths are much smaller than collisional mean free paths and a variety of kinetic phenomena are seen at the shock fronts according to in situ observations of planetary shocks. Hence, both the MHD and kinetic equations have been adopted in theoretical and numerical studies to describe different aspects of the physical phenomena associated with astrophysical shocks. In this paper, we present the results of 3D relativistic particle-in-cell (PIC) simulations for ion-electron plasmas, with focus on the shock structures: when a jet propagates into an unmagnetized ambient plasma, a shock forms in the nonlinear stage of the Weibel instability. As the shock shows the structures that resemble those predicted in MHD systems, we compare the results with those predicted in the MHD shocks. We also discuss the thermalization processes of the upstream flows based on the time evolutions of the phase space and the velocity distribution, as well as the wave spectra analyses.

• 천문학회지
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• 제46권5호
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• pp.183-190
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• 2013

Recurring jets, which are jets ejected from the same site, are a peculiar type among various solar jet phenomena. We report such recurring jets ejecting from the same site above an active region on January 22, 2012 with high-resolution multi-wavelength observations from Solar Dynamics Observatory(SDO). We found that the recurring jets had velocities, lengths and lifetimes, but had similar directions. The visible brightening appeared at the jet base before each jet erupted. All the plasma produced by the recurring jets could not overcome the large coronal loops. It seemed that the plasma ejecting from the jet base was confined and guided by preexisting coronal loops, but their directions were not along the paths of the loops. Two of the jets formed crossing structures with the same preexisting filament. We also examined the photospheric magnetic field at the jet base, and observed a visible flux emergence, convergence and cancellation. The four recurring jets all were associated with the impulsive cancellation between two opposite polarities occurring at the jet base during each eruption. In addition, we suggest that the fluxes, flowing out of the active region, might supply the energy for the recurring jets by examining the SDO/Helioseismic and Magnetic Imager (HMI) successive images. The observational results support the magnetic reconnection model of jets.

• 천문학회보
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• 제44권1호
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• pp.42.2-42.2
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• 2019

Turbulence is one of the natural phenomena in molecular clouds. It affects gas density and velocity fluctuation within the molecular clouds and controls the mode and tempo of star formation. However, despite many years of study, the properties of turbulence remain poorly understood. As part of the Taeduk Radio Astronomy Observatory (TRAO) Key Science Program (KSP), "mapping Turbulent properties In star-forming MolEcular clouds down to the Sonic scale (TIMES; PI: Jeong-Eun Lee)", we have fully mapped two star-forming molecular clouds, the Orion A and the Ophiuchus molecular clouds, in 3 sets of lines ($^{13}CO$ J=1-0, $C^{18}O$ J=1-0, HCN J=1-0, $HCO^+$ J=1-0, CS J=2-1, and $N_2H^+$ J=1-0) using the TRAO 14-m telescope. We apply a statistical analysis, Principal Component Analysis (PCA), which can recover an underlying turbulent-power spectrum from an observed P-P-V spectral map. We compare turbulence properties not only between the two clouds, but also between different parts within each cloud. We present the first result of our observation program.

• 천문학논총
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• 제27권4호
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• pp.217-218
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• 2012

Among the AKARI all-sky survey data, the $9{\mu}m$ diffuse map is crucial to study the polycyclic aromatic hydrocarbon (PAH) emission features on large spatial scales, while the $18{\mu}m$ map is useful to trace hot dust emission. To utilize these advantages, we have improved the AKARI mid-infrared (MIR) all-sky survey diffuse maps. For example, we have established special methods to remove the effects of the ionizing radiation in the South Atlantic Anomaly (SAA) and of the scattered light from the moon. Using improved diffuse map data, we study the properties of PAHs and dust in the Galactic center region associated with high-energy phenomena.

• 천문학회지
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• 제36권spc1호
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• pp.109-115
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• 2003

We report the results of the ionospheric measurement obtained from the instruments on board the Korea Multi-Purpose Satellite - 1 (KOMPSAT-l). We observed a deep electron density trough in the nighttime equatorial ionosphere during the great magnetic storm on 15 July 2000. We attribute the phenomena to the up-lifted F-layer caused by the enhanced eastward electric field, while the spacecraft passed underneath the layer. We also present the results of our statistical study on the equatorial plasma bubble formation. We confirm the previous results regarding its seasonal and longitudinal dependence. In addition, we obtain new statistical results of the bubble temperature variations. The whole data set of measurement for more than a year is compared with the International Reference Ionosphere (IRI). It is seen that the features of the electron density and temperature along the magnetic equator are more prominent in the KOMPSAT-l observations than in the IRI model.