• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.106.1-106.1
• /
• 2012

The Gegenschein is a faint glow around the anti-solar point caused by the interplanetary dust particle(IDP)'s back-scattering enhancement. From the previous low resolution observations, the overall morphology of the Gegenschein has been intensively studied. However, sub-degree scale fine structure of the Gegenschein is still not well known, even though the detailed morphology of the Gegenschein within a few degree from the anti-solar point may supply pivotal information about the property of the IDPs. We made optical CCD observations of the Gegenschein between 2003 March and 2006 November. From the observations, we succeeded in making high resolution images of the Gegenschein, with unprecedented 1.'4 resolution. Our results concur with IDP cloud model based on the infrared observations combined with scattering phase function derived from low resolution data. The only exception is the anti-solar point. We found a steep additional brightness enhancement existing at the exact anti-solar point. Plausible explanation of the finding is that the IDPs are significantly larger than observing wavelength, and have irregular morphology or inhomogeneous internal structure. Furthermore, we measured average geometric albedo of the IDPs from the optical brightness of the anti-solar point. The geometric albedo was $0.06{\pm}0.01$, similar to those of comets or C-type asteroids.

• Publications of The Korean Astronomical Society
• /
• v.33 no.3
• /
• pp.31-44
• /
• 2018

Song, I-Yeong (1619 ~ ?) was an active astronomer in the Joseon dynasty at the era of adopting the Shixian-li, Chinese calendar in Qing dynasty. His astronomical contribution was recorded in Annals of the Joseon Dynasty, Diary of the Royal Secretariat, Comparative Review of Records and Documents-Its Revision and Enlargement, and Treatise on the Bureau of Astronomy. In addition the details on his life and works were found at the genealogies of the Song Family from Yeonan and the Kim Family from Seonsan. His major astronomical activities can be summarized in three items. First, as a specialist astronomer, he has attempted to make a systematic observation of two comets. Second, he designed and fabricated the Jamyeong-jong, the weight-powered armillary clock, which became a typical model of the astronomical clock in the Joseon dynasty. Last, he served as a royal astronomical professor, greatly contributing on implementing the Shixian-li. Song has concentrated on performing astronomical duties for his royal official service time. Song is regarded as an important astronomer who made it possible to enforce the Shixian-li until the late Joseon dynasty.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.2
• /
• pp.44.2-44.2
• /
• 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.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.1
• /
• pp.56.3-57
• /
• 2015

As of early 2015, more than 12,000 Near-Earth Objects (NEOs) have been catalogued by the Minor Planet Center, however their observational properties such as broadband colors and rotational periods are known only for a small fraction of the population. Thanks to time series observations with the KMTNet, orbits, optical sizes (and albedo), spin states and three dimensional shapes of asteroids and comets including NEOs will be systematically investigated and archived for the first time. Based on SDSS and BVRI colors, their approximate surface mineralogy will also be characterized. This so-called DEEP-South (Deep Ecliptic Patrol of the Southern Sky) project will provide a prompt solution to the demand from the scientific community to bridge the gaps in global sky coverage with a coordinated use of the network of ground-based telescopes in the southern hemisphere. We will soon finish implementing dedicated software subsystem consisted of automated observation scheduler and data pipeline for the sake of increased discovery rate, rapid follow-up, timely phase coverage, and efficient data analysis. We will give a brief introduction to test runs conducted at CTIO with the first KMTNet telescope in February and March 2015 and experimental data processing. Preliminary scientific results will also be presented.

• Environmental Mutagens and Carcinogens
• /
• v.21 no.2
• /
• pp.89-94
• /
• 2001

Recently, single cell gel electrophoresis, also known as comet assay, is widely used for the detection and measurement of DNA strand breaks in vitro and in vivo in many toxicological fields such as radiation exposure, human monitoring and toxicity evaluation. As well defined, comet assay is a sensitive, rapid and visual method for the detection of DNA strand breaks in individual cells. Briefly, a small number of damaged cells suspended in a thin agarose gel on a microscope slide were lysed, unwinded, electrophoresed, and stained with a fluorescent DNA binding dye. The electric current pulled the charged DNA from the nucleus such that relaxed and broken DNA fragments migrated further. The resulting images which were subsequently named for their appearance as comets, were measured to determine the extent of DNA damages. However, some variations could be occurred in procedures, laboratories's conditions and kind of cells used. Hence, to overcome and to harmonize these matters in comet assay, International Workshop on Genotoxicity Test Procedure (IWGTP) was held with several topics including comet assay at Washington D.C. on March, 1999. In spite of some consensus in procedures and conditions in IWGTP, there are some problems still remained to be solved. In this respect, we attempted to set the practical optimal conditions in the experimental procedures such as lysis, unwinding, electrophoresis and neutralization conditions and so on. First of all, we determined optimal lysis and unwinding time by using 150 $\mu$M methyl methanesulfonate (MMS) which is usually used concentration. And then, we determined optimal positive control concentrations of benzo(a)pyrene (BaP) and MMS in the presence and absence of S9 metabolic activation system, respectively.

• Journal of Astronomy and Space Sciences
• /
• v.22 no.3
• /
• pp.293-310
• /
• 2005

We made a revised catalogue for reliable records of meteor outbursts that were recorded in Korean, Japanese, and Chinese chronicles. In order to avoid the effects of both Earth's precession and perihelion shift, we introduced a new time-coordinate of records, or the number of days elapsed within the sidereal year of the record for a given origin of time or the perihelion passage time of the you 2000. We added nineteen new records of meteor showers that are wrongly classified i, individual meteors in a Chinese archive. We found that the ${\eta}-Aquarids,$ the Perseids, the Orionids, and the Leonids have been active during the last two millennia. Due to the change of time-coordinate, the oldest record of each long-lasting meteor shower has been slightly corrected. We discuss that these long-lasting meteor showers belong to the Halley-type comets.

• Proceedings of the Korea Society of Environmental Toocicology Conference
• /
• 1997.12a
• /
• pp.101-101
• /
• 1997

Comet assay, single cell gel electrophoresis has been known as useful, rapid, simple, visual, and sensitive technique for measuring the DNA breakage in mammalian ce1ls. For evaluation of DNA damage using comet assay, early studies reported a change in comet length and intensity with DNA damage using simple visual technique, such as fluorescence microscopy with eyespiece. In recent, some workers are observing and analyzing nucleotide of comets using quantitative fluorescence image analysis system to estimate 'tail moment', which is defined as the product of the tail length and the fraction of total DNA in tail. Our laboratory also adopted the image analysis software for qualification. In addition, many of the practical features of comet assay render it potentially attractive as useful tool for molecular toxicology and carcinogenesis, because the system is already showing considerable promise as rapid predictor in both in vitro and in vivo experimental designs. Recently, the comet assay becomes a attractive technique to study of apoptosis, because apoptotic fragmentation of nuclear DNA into nucleosomal sizes can be evaluated by the comet assay. So, we attempted to apply the comet assay to studying the effect of various stress on the apoptosis-sensitive cell lines. Particularly, focusing on the hyperthermic apoptosis, we could find that heat shock(44˚C for 60 minutes) was sufficient to induced apoptosis in these cell lines. But using the highly sensitive comet assay, we could not detect DNA breaks immediately after heat shock.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.2
• /
• pp.50.2-50.2
• /
• 2016

Polarization is a rich source of information on the physical properties of astronomical objects. In particular, scattered sunlight by optically thin media (e.g., cometary comae) shows linear polarization of light, which highly depends on the phase angle (an angle between the Sun-Comet-Earth), wavelengths, and physical properties of cometary dust particles such as size, composition, and structures. Here, we present a study of polarimetric properties of non-periodic comet C/2013 US10 (Catalina) in optical and near-infrared wavelength regions obtained from imaging, spectroscopy, and polarimetric observations taken on UT 2015 December 17 - 19 welcoming its (probably) first close approach to the Earth. In this presentation, we want to introduce our progress since the last Korean Astronomical Society meeting (at BEXCO, Busan, 2016 April 14 - 15) especially in terms of spatial variations of degree of linear polarization (DOLP) and its possible scenarios to explain the correlations with other observational results. In particular, we found that there is strong anti-correlation between the gas/dust flux ratio and DOLP at the cometocentric distance of $(2-5){\times}104 km$. Besides, within 10 arcseconds in radii (corresponding to inner coma region of 104 km from the center), the inverse relationship of these two parameters does not hold anymore. We conjecture that the rapid outward increase of DOLP can be supported by either the sublimation/evaporation of icy volatiles, disaggregation of cometary dust particles ejected from the nucleus, and/or difference of dominant dust particle sizes. From our results, we can conclude that comet C/2013 US10 (Catalina) corroborates rather indefinite traditional classification of poalrimetric classes of comets, and provides good opportunity to study less processed material which probably cherishes its memory at the formation epoch of the Solar System.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.2
• /
• pp.48.2-48.2
• /
• 2016

The wide-field and the round-the clock operation capabilities of the KMTNet enables the discovery, astrometry and follow-up physical characterization of asteroids and comets in a most efficient way. We collectively refer to the team members, partner organizations, the dedicated software subsystem, the computing facility and research activities as Deep Ecliptic Patrol of the Southern Sky (DEEP-South). Most of the telescope time for DEEP-South is devoted to targeted photometry of Near Earth Asteroids (NEAs) to push up the number of the population with known physical properties from several percent to several dozens of percent, in the long run. We primarily adopt Johnson R-band for lightcurve study, while we employ BVI filters for taxonomic classification and detection of any possible color variations of an object at the same time. In this presentation, the progress and new findings since the last KAS meeting will be outlined. We report DEEP-South preliminary lightcurves of several dozens of NEAs obtained at three KMTNet stations during the first year runs. We also present a physical model of asteroid (5247) Krylov, the very first Non principal Axis (NPA) rotator that has been confirmed in the main belt (MB). A new asteroid taxonomic classification scheme will be introduced with an emphasis on its utility in the LSST era. The progress on the current version of automated mover detection software will also be summarized.

• Journal of The Korean Association For Science Education
• /
• v.24 no.5
• /
• pp.886-901
• /
• 2004

The purpose of this study was to document the changes in astronomical concepts for preservice and inservice elementary school teachers after being presented with the newly devised Earth Motions Centric Solar System Model. The subjects of the study were 31 preservice and 30 inservice elementary schools teachers in the Jeonbuk Province. First, the author investigated the naive theories of the subjects, and then, compared that data to the data obtained after their exposure to the model. The total number of items on the instrument for this study was 10. These items included questions about the motion of interior planets, the phases and sizes of interior planets, and the motion of exterior planets and comets. After analyzing the answers to the items before the experiment, the author was able to confirm the existence of the naive theories regarding astronomical phenomena. Also, after the experiment, the author was able to observe the conceptual change in thought of the preservice and inservice elementary school teachers. Results showed that learning through the new model had positive effects on the preservice and inservice elementary school teachers' conceptualization of the interior planets' motion, phases and sizes, and the exterior planets' motion.