• 천문학논총
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• 제30권2호
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• pp.767-768
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• 2015

Spectra of reflected sunlight from Mars and Jupiter are presented. They were obtained from an educational 1-D array spectrograph covering almost a full range of visible wavelengths, 200~900 nm with 1 nm spectral resolution. The question was whether a spectral difference could be obtained between that of terrestrial planets and gas planets with an educational spectrograph. It was installed in a 12-inch reflecting telescope at the Korea Science Academy of KAIST in Busan. Both spectra show clear absorption lines of reflected sunlight. They shows differences oin line presence, but are not very significant. This work means that the spectrograph successfully observed the reflected spectra of planets and can detect differences in spectra in terms of the absence and presence of absorption lines of planets.

• 산업진흥연구
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• 제8권4호
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• pp.221-227
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• 2023

본 연구는 고전점성학(Classic Astrology)의 네이티비티(Nativity) 출생차트에서 그 차트를 구성하고 있는 행성들의 기능과 구조를 살펴 네이티비티의 직업적성을 분석하는 연구이다. 즉 출생차트에서 나타나는 직업을 개인의 타고난 직업으로 본다면 사인(Sign, 별자리)과 플래닛(Planets, 행성)의 강약, 애스펙트(행성과의 관계) 등을 통하여 분석한다. 고전점성학(Classic Astrology)의 네이티비티(nativity) 출생차트에서는 직업을 판단할 때 크게 세 개의 플래닛인 금성(♀. Venus). 화성(♂. Mars). 수성(☿. Mercury)에 의하여 결정된다고 보았다. 그러나 현대에 와서 고도로 발전된 지식정보화 사회에서 요 구되는 직업의 다양성에 부합하기 위해서는 조금 미흡한 점이 있어 토성(♄. Saturn), 목성(♃. Jupiter), 태양(☉. Sol), 달(☽. Luna)을 더하여 직업의 적성을 적용하였다. 그 결과로 네이티브의 ASC의 직업적성을 플래닛과 그들의 애스펙트 관계를 토대로 더욱 다양하고 폭넓은 적용이 가능하였다. 그 결과 금성(♀. Venus)은 사람들이 아름답다고 생각하는 예술성이 있는 일을 즐기며 그것을 삶의 낙으로 삼을 수 있는 일을 의미하였으며, 화성(♂. Mars)은 노동일과 같이 체력과 힘을 쓰는 일을 의미한 것을 알 수 있었다. 또 수성(☿. Mercury)은 지식과 두뇌를 활용하는 일을 의미하고 있으며, 태양(☉. Sol)은 직업과 재능에 권위를 부여해주는 역할을 하고 있고, 달(☽. Luna)은 네이티브의 직업과 재능에 사람들의 신뢰를 얻도록 해주었으며 목성(♃. Jupiter)은 믿음과 성실함, 공정함, 너그러움 등이 네이티브의 직업과 재능을 살리는데 도움을 주었으며, 토성(♄. Saturn)은 탐욕, 슬픔, 궁핍함 등으로 직업과 재능을 가로막는 장애로 나타날 수 있었고. 결과적으로 플래닛의 강약과 그 플래닛들의 애스펙트 관계에 따라 네이티브의 직업이 다양하게 나타남을 알 수 있었다.

• 천문학회보
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• 제35권2호
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• pp.78.1-78.1
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• 2010

We obtained the spectra of 93 Planet host stars and 73 normal field stars in F, G, K type using BOES at BOAO. We measured the equivalent width of Fe and 13 elements lines using the automatic EW measurement program, TAME(Tools for Automatic Measurement of Equivalent-widths) and estimated the abundances by synth and abfind driver of MOOG code. Since the absence of planets in the normal field stars cannot be "completely" proved, this work focused on the chemical abundances and planet properties of planet host stars, which have the massive planets close to the parent star relatively. We carried out an investigation for the difference of abundances between stars with "Hot Jupiter" and normal field stars with no known planets. We examined the chemical composition of 12 elements, such as Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni by EW measurements, and the S abundances were estimated using synthetic spectrum.

• 천문학회보
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• 제36권1호
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• pp.27.1-27.1
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• 2011

We obtained the spectra of 93 Planet host stars and 73 normal field stars in F, G, K type using BOES at BOAO. We measured the equivalent width of Fe and 25 elements lines using the automatic EW measurement program, TAME(Tools for Automatic Measurement of Equivalent-widths) and estimated the elemental abundances by synth and abfind driver of MOOG code. Since the absence of planets in the normal field stars cannot be "completely" proved, this work focused on the chemical abundances and planet properties of planet host stars, which have the massive planets close to the parent star relatively. We carried out an investigation for the difference of abundances between stars with "Hot Jupiter" and normal field stars with no known planets. We examined the chemical composition of 25 elements, such as C, N, O, S, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Eu by EW measurements, and the S abundances were estimated using synthetic spectrum. We have found that [Mg/Fe] and [Al/Fe] for planet host stars have lower limit comparing with those of comparison stars, and [Ca/Fe] of host star with Neptunian planets is relatively lower than the other host stars with massive planets. We have performed the Kolmogorov-Smirnov test, and examined the ratio of planet host stars to all stars for each bin of [X/H]. As a result, we noted that the O, Si, and Ca abfor undances are strongly related with the presence of planets.

• Monthly Notices of the Royal Astronomical Society
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• 제480권3호
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• pp.4183-4198
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• 2018

Rings have recently been discovered around the trans-Neptunian object (TNO) 136108 Haumea and the Centaur 10199 Chariklo. Rings are also suspected around the Centaur 2060 Chiron. As planetary close encounters with ringed small bodies can affect ring longevity, we previously measured the severity of such encounters of Chariklo and Chiron using the minimum encounter distance, d_min. The value of d_min that separates noticeable encounters from non-noticeable encounters we called the 'ring limit', R. R was then approximated as 10 tidal disruption distances, 10R_td. In this work, we seek to find analytical expressions for R that fully account for the effects of the planet mass, small body mass, m_s, ring orbital radius, r, and velocity at infinity, v_∞, for fictitious ringed Centaurs using ranges 2 × 10²⁰ kg ≤m_s≤ 1 Pluto mass and 25 000 ≤r ≤ 100 000 km. To accomplish this, we use numerical integration to simulate close encounters between each giant planet and ringed Centaurs in the three-body planar problem. The results show that R has a lower bound of approximately 1.8R_td. We compare analytical and experimental R values for a fictitious Haumea, Chariklo, and Chiron with r= 50 000 km. The agreement is excellent for Haumea, but weaker for Chariklo and Chiron. The agreement is best for Jupiter and Saturn. The ring limits of the real Haumea, Chariklo, and Chiron are <4R_td. Experimental R values for the fictitious bodies make better approximations for the R values of the real bodies than does 10R_td. Analytical values make good first approximations.

• 천문학논총
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• 제30권2호
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• pp.761-763
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• 2015

Colors have been derived from the observed optical spectrum of Mars and Jupiter. It is known that the planets and the Moon emit reflected sunlight and thus their spectra are similar to the spectrum of solar radiation. The question was then why is the color of Mars different from that of other planets, i.e. red, although it would share the same spectrum of reflected sunlight. Can one derive color from the spectrum? Therefore, we observed the optical spectra of the scattered sunlight in day time for the Moon and Mars using a 1-D array spectrograph on the 12-inch reflecting telescope in the Korea Science Academy of KAIST in Busan, Korea. We adopted the International Commission on Illumination (CIE) in 1931 of three spectral sensitivity peaks for the human eye in short, medium and long wavelengths in visible light. The observed spectra were imposed on CIE sensitivities and the color detected by the human eye was derived. The Mars spectrum represents red color and the Moon white. It is a similar color to that which a human would see. This result means that color is easily derived from astronomical spectra. The appearance of the planets surface can be determined for Mars, which is the result of iron oxide.

• 천문학논총
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• 제30권2호
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• pp.61-64
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• 2015

The brightness of Io's magnetic footprint, an indicator of electromagnetic interaction at the satellite, appears to be strongly connected to the satellite's distance from the plasma equator. As a result, the brightest footprints were detected when Io is near the interception location between the satellite's orbital plane and the plasma equator. However, volcanic activities on Io show strong correlation with the equatorward shift of Jupiter's main auroral oval, consequently causing the disappearance of Io's footprint. The same conclusion was suggested via the observation of Jupiter's hectometric radio emission, called HOM, which closely corresponds to Jupiter's auroral activity. The plasma environment near the Jovian satellites was found to vary significantly at different observational epochs. The electron density increased by approximately a factor of three from the Voyager epoch (1979) to the Galileo epoch (1995), while the electron density was found to be significantly higher (~ 5 times) in the Cassini epoch (2001). In this current study, the magnetic footprints were clearly brighter ten years ago (from peak brightness in 1998-2001) than the footprints detected in 2007. For volcanic activities on Io in 2007, there are two clear activities in February and late May. The magnetic footprint appeared to be dimmer in March 2007, expected to be the result of volcano activities in Feb 2007. However, the magnetic footprint brightness in June appeared to be slightly brighter than the footprints observed in May. The reason could be the time delay between the brightening of the sodium nebula on approximately May 31st and, a while later, the enhancement of flux tube content peaking on approximately June 5th. On the other hand, Io's magnetic footprints were observed during June 1st - 10th when they may not yet have been affected by the increase in mass outflow due to the increase of plasma density.

• 천문학회보
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• 제35권1호
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• pp.48.2-48.2
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• 2010

Korean-Japanese Planet Search Program has been carried out since 2005 to search for planets around intermediate-mass giant stars (1.5-5.0 solar masses) by an international collaboration between Korean and Japanese researchers. In this program, we have been carrying out a precise radial velocity survey of about 190 G-type giant stars (6.21.9 solar masses) giant stars. These results extend the planet mass distribution of massive intermediate-mass stars to higher and lower mass region, and may further constrain substellar system formation mechanisms. We report the recent results and current status of Korean-Japanese Planet Search Program.

• 천문학회지
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• 제29권spc1호
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• pp.351-354
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• 1996

In this paper it is explained how most of asteroids can avoid very close approach to Jupiter, to the earth for earth orbit crossing asteroids, and to Neptune for Kuiper-belt asteroids by mechanisms which work also for Neptune-Pluto system. In fact the mutual distance of the planets cannot become very small as the critical argument librates around $180^{\circ}$ because of 2:3 mean motion resonance and the argument of perihelion of Pluto librates around $90^{\circ}$. And it is found that among nearly 40 Kuiper-belt asteroids discovered in recent years $40\%$ have orbits similar to Pluto. For main-belt asteroids the distribution with respect to the semi-major axes has peculiar characteristics and the author tries to explain how their peaks and gaps are created. It is also found that $30\%$ of 80 earth orbit crossing asteroids which have minimum perihelion distances less than 1.04AU have no chance to collide with the earth. Still $30\%$ of them have a few probability to collide with the earth as they have dynamical characteristics of short-periodic comets.

• 천문학회보
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• 제42권2호
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• pp.48.3-49
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• 2017

Interplanetary space of the solar system contains a large number of dust particles, referred to as Interplanetary Dust Particles (IDPs) cloud complex. They are observable through meteors and zodiacal lights. The relative contribution of possible sources to the IDPs cloud complex was an controversial topic, however, recent research (Yang & Ishiguro, 2015 and references therein) suggested a dominance of cometary origin. In this study, we numerically investigated the orbital evolution of cometary dust particles, with special concerns on different evolutionary tracks and its consequences according to initial orbits, size and particle shape. The effect of dust particle density and initial size-frequency distribution (SFD) were not decisive in total cloud complex mass and mass supply rate, when these physical quantities are confined by observed zodiacal light brightness and dust particle SFD at 1 au. We noticed that, if we assume the existence of fluffy aggregates discovered in the Earth's stratosphere and the coma of 67P/Churyumov-Gerasimenko, the required mass supply rate decreases significantly. We also found out that close encounters with planets (mostly Jupiter) are the dominating factor of the orbital evolution of dust particles, as the result, the lifetime of cometary dust particles are shorter than Poynting-Robertson lifetime (around 250 thousand years). As another consequence of severe close encounters, only a small fraction of cometary dust particles can be transferred into the orbit < 1 au. This effect is significant for large size particles of ${\beta}$ < 0.01. The exceptional cases are dust particles ejected from 2P/Encke and active asteroids. Because they rarely encounter with Jupiter, most dust particles ejected from those objects are governed by Poynting-Robertson effect and well transferred into the orbits of small semimajor axis. In consideration of the above effects, we directly estimated probability of mutual collisions between dust particles and concluded that mutual collisions in the IDPs cloud complex is mostly ignorable, except for the case of large sized particles from active asteroids.