TBA

In this talk, recent advances on space telescope pointing technologies for fine imaging performance of telescope are introduced. The special emphasis is on Hubble Space Telescope and James Webb Space Telescope. FGS(Fine Guidance Sensor) onboard HST and JWST is highlighted as a crucial component for  the spectacular scientific achievement. In particular, Cubesat-based telescope and precise pointing with commercial-off-the-shelf products are addressed. Recommendation on future research are made to enhance domestic technology level.

The Square Kilometre Array, a 21st Century mega-facility, is under construction in both Australia and South Africa. After a 35-year journey construction is well underway; I shall describe the scientific promise of SKA, the current construction status and provide a hint of what is to come.

NASA 중형 우주망원경 미션인 SPHEREx는 세계 최초로 적외선 영상분광 탐사를 수행하여 우주의 기원, 은하의 형성과 진화, 생명 기반 물질 탐사 등 주요 과학연구 주제를 연구할 계획이다. 한국천문연구원은 유일한 국제협력기관으로 하드웨어 개발, 자료처리 파이프라인 구축, 과학연구 등 전 분야에 걸쳐 기여하고 있다. SPHEREx는 최근 성공적으로 발사되어 초기 운영이 진행 중으로. 이번 콜로키움에서는 그동안 있었던 SPHEREx 프로젝트 현황과 앞으로 수행될 관측 운영 및 활용 연구 등에 대해 개략적으로 소개하고자 한다.

The structure and kinematics of the gas around galaxies are crucial for understanding the multiphase flows within the galactic ecosystem and, thus, galaxy evolution and star formation as a whole. Traditionally, insights into the structure of the circumgalactic medium (CGM) have been investigated through absorption line studies. Recent advancements in instruments and techniques, however, offer a new perspective on gas flows around galaxies through emission features of resonance lines, such as  Hydrogen Lyman-α (Lyα at 1215.67 Å), and metal resonance lines, such as Mg II λλ2796, 2803, C IV λλ1548, 1551, O VI λλ1032, 1038. These resonance lines act as coolants of shocked gas by collisional excitation and ionized gas by recombination. Furthermore, due to their resonance nature, the physical properties of scattering regions are imprinted on their observables. For example, Lyα emission includes the information of the H II region intrinsically and the H I region through scatterings. Other metal resonance lines also carry the properties of emission and scattering regions. In particular, the Mg II resonance line has emerged as a promising tracer of cold gas at T ~ 10^4 K like Lyα. To decode the message in their observations, I have developed a 3D Monte-Carlo radiative transfer code ‘RT-scat’. In this talk, I will introduce the CGM and the radiative transfer of resonance lines. I will also present how Mg II emission lines form in various environments, including inflowing/outflowing. Furthermore, I will discuss how to explore cold gas properties through observations of Mg II resonance lines. If time allows, I will also discuss other UV metal resonance lines as tracers of multiphase gas.

 The optical properties, chemical composition, and structure of materials on the surfaces of airless bodies in the Solar System, such as the Moon and asteroids, are altered by cosmic-ray irradiation, including solar wind and galactic cosmic rays, as well as by micrometeorite bombardment. These processes are collectively known as space weathering, which is why the differences exist between telescopic observations of asteroids and meteorites in reflectance and spectral properties. The regolith of the surface experienced shattering, abrasion, and compression for a long-lived history of the bodies. Sometimes, dust particles lofted by impact or electrostatic force cover the surface on top of the regolith. The situation gets more complicated once volatiles, such as water, are involved. These complex processes are impossible to reproduce or simulate on Earth comprehensively, even with the samples from the Moon and asteroids. A new approach, such as polarimetry using PolCam, onboarded Danuri, and GrainCams for NASA CLPS, the Commercial Lunar Payload Service program, will contribute to understanding the regolith's surface structure and properties. In this opportunity, I will also introduce the scientitic motivations of LUSEM, LSMAG, and LVRAD instruments for NASA CLPS and discuss future lunar exploration plan updates.

The stellar obliquity, a probe to planet migration history, is the angle between the rotation axis of the host star and the normal of the orbital plane of the planet. Various migration theories with different timescales, e.g., primordial disk misalignment (< 3 Myr), Kozai-Lidov mechanism (10^4-10^8 yr), secular chaos (10^7-10^8 yr), differ strongly in their predictions on the obliquity. These mechanisms all functions during the youth of the planetary systems (< 1Gyr). Therefore, young planetary systems are the promising targets to constrain the models and timescales of planetary formation and migration. In the presentation, we will briefly introduce measuring stellar obliquity of planets in the young systems with high-resolution spectroscopy and extreme-precise radial velocity. 

본 세미나에서는 우리나라의 심우주탐사 개발현황에 대해 소개한다. 특히 약 50kg급 초소형, 저가형 시연기(STD 1.0)을 활용하여 우리나라가 심우주탐사, 특히 태양-지구 L4/L5, 소행성, 화성탐사가 가능한지 궤적설계 Trade-off study를 통해 살펴본다.

우주산업은 민간 주도의 '뉴 스페이스' 시대로 패러다임이 전환되고 있다. 이러한 변화 속에서 급변하는 글로벌 우주산업 동향을 살펴보고, 변화의 시대에 적합한 우리의 대응 방안을 모색하기 위해 주목할 시사점을 짚어본다. 뉴 스페이스를 대표하는 소형위성과 소형발사체의 시장 동향과 해외 개발 사례를 통해 후발주자로서 우리나라가 글로벌 우주발사체 시장에 진입하기 위해 필요한 전략과 가능성을 탐구한다. 국내 소형발사체를 개발 중인 이노스페이스의 기술 개발 및 사업화 현황을 소개하고, 뉴 스페이스 시대에 국내 우주 스타트업으로서 마주한 도전과 기회를 조명한다.

The Korea Institute of Photonics and Technology is at the forefront of optical research, particularly in the development of advanced optical materials. This presentation focuses on ceramic optical materials characterized by very low thermal expansion coefficients, which are crucial for large-diameter mirror applications in space telescopes. We will examine several materials, including ZERODUR, ULE, CLEARCERAM-Z, and SiC, which are commonly used in optical devices for space applications.

We will discuss the manufacturing processes and unique properties of these low-expansion materials, along with practical case studies showcasing the production of large telescope mirror materials. Furthermore, the presentation will provide an overview of the current technological advancements in low expansion materials, highlighting their significance in enhancing the performance of astronomical instruments.

This presentation provides an overview of South Korea’s first lunar exploration mission, the Korea Pathfinder Lunar Orbiter (KPLO), also known as Danuri. Launched on August 4 (KST), 2022, KPLO marked South Korea’s first successful attempt to send an orbiter to the Moon, representing a significant milestone in the country’s space exploration journey. The primary objectives of the KPLO mission include conducting scientific lunar observations, testing space technologies, and demonstrating South Korea’s capability for deep space exploration.

In this session, we will discuss the development and operation process of Danuri, followed by the results achieved from its scientific payloads so far. We will also share the lessons learned throughout all phases of the KPLO mission. Key topics will include programmatic and technical challenges, collaboration with NASA, and experiences from the KPLO operation. These discussions will provide valuable perspectives on our current space exploration capability and contribute to preparing South Korea’s future space exploration endeavors.

KAI 항공우주 사업 소개 및 비전 제시

Recent 3-7σ detections of parity asymmetry in the observed galaxy distribution have spurred interest in searching for potential signals of primordial parity violation. In this talk, I will explore the possibility of detecting parity-violation in primordial vector fossils using late-time galaxy spins. By leveraging N-body simulations, we employ halo spins as proxies for galaxy spins to examine the persistence of primordial vectorial parity asymmetry at low redshifts. Our method introduces a novel approach to generate initial conditions with significant parity asymmetry while keeping the initial matter power spectrum unchanged. By analyzing the helicity of the initial spin and halo spin vector fields, we detect substantial asymmetry in the initial spin field due to primordial vectorial parity violation, with over 50% of this asymmetry surviving in the late-time halo spin field across a range of scales. I will discuss the cosmological implications of our findings and conclude with prospects using galaxy surveys.

Integral field galaxy surveys have discovered that galaxy spin (the relative contribution of rotation and random motion to dynamical support) depends on environment, galaxy mass and stellar population age. However, the key drivers have remained obscured. I will introduce the SAMI Galaxy Survey and use these data across a multi-dimensional parameter space to show that stellar population age is the dominant driver of galaxy spin. In fact, across our sample, once the relation between light-weighted age and spin is accounted for, there is no significant residual correlation between spin and mass, or spin and environment. This result is strongly suggestive that present-day environment only indirectly influences spin, via the removal of gas and star formation quenching. That is, environment affects age, then age affects spin. Older galaxies then have lower spin, either due to stars being born dynamically hotter (progenitor bias) at high redshift, or due to secular heating. The only regime in which environment plays a role in setting spin is for high-mass (log(M*)>11) galaxies, where there is a residual environmental trend with central galaxies preferentially having lower spin, compared to satellites of the same age and mass. We argue that this trend is likely due to central galaxies being a preferred location for mergers. 

We have undertaken a multidisciplinary study of the thermal decomposition of Murchison CM2 carbonaceous chondrite as an analog to metamorphic process that may have occurred on carbonaceous asteroids. The pre- and post-heated Murchison powders were analyzed using X-ray diffraction, thermal and evolved gas analysis, visible-near-infrared spectroscopy, microto nanoscale analyses included scanning and transmission electron microscopy. Mineralogical analyses of the unheated Murchison samples identified fine-grained serpentine, rounded Mg-rich serpentine (chrysotile-type), platy Fe-rich serpentine (cronstedtite-type), tochilinite, tochilinite-cronstedtite intergrowths, olivine, pyroxene, iron-nickel sulfides, magnetite, potassium iron-nickel sulfide, calcite, gypsum, apatite, Cr-bearing spinel, and chromite. The tochilinite shows the contorted morphology, mainly showing (002) lattice fringes of ~5.4 Å spacing and the identification of a new twinning relationship on the (032) plane. In response to thermal effects, serpentine group minerals are converted into mixtures of sub-μm olivine and pyroxene grains with similar Mg/Mg+Fe ratios as the precursor. Tochilinite breakdown forms troilite, magnetite, and minor Fe-Ni metal aggregates via amorphization. The thermal processing of Murchison carbonaceous chondrite produces distinctive micron and submicron structures that correspond to the breakdown of key minerals. These findings will be useful for understanding the thermal history of carbonaceous asteroids and for analyzing samples returned from ongoing missions to primitive asteroids (101955) Bennu and (162173) Ryugu.

During the last decades, the heliospheric studies significantly contributed to our understanding of how the Sun’s magnetic acitivity affects the space weather of Earth in the short term and its climate change in the intermediate term. It now seems quite timely or urgent to extend this expersise to resolve two outstanding problems: 1) how the solar magnetic activity have affected the habitability of Earth and other planets in the long term, and 2) how the magnetic acivity of a star affects the habitability of an exoplanet orbiting around the star. Resolving these two problems are intimately related to revealing of the fundamental principle and diversity of dynamo process in a variety of stars, planets and satellites. A useful tool for these scientific goals is comparative heliospheric studies: comparing Earth and Mars, comparing the present Sun-Earth system and the past system, comparing solar magnetic activity and stellar magnetic activity. Comparing flares between the Sun and other stars has become very active in the last decade, and comparing prominence eruptions between the Sun and stars is becoming popular, as prominnece eruptions are regarded as a signature of coronal mass jections that can be observed from the ground. In this talk, I will review the recent observations of flares and prominence eruptions on EK Dra that is regarded as a “young Sun”, in comparison with those on the Sun. We conclude that detecting prominence eruptions on a magnetically active star is much more difficult to detect flares, and would require high S/N spectroscopy as well as a reasonable model of radiation on the star during the eruptions.

I report on methods for the estimation of stellar parameters and elemental abundances, including [Fe/H], [C/Fe], and [Mg/Fe], for very large samples of stars in the disk and halo of the Milky Way, making use of a combination of narrow-band photometry from the J-PLUS and S-PLUS surveys and broad-band photometry from Gaia DR3. The techniques employed can achieve estimates with precisions that are commensurate with that obtained from low- and medium-resolution spectroscopy. I summarize the identification of on the order of 0.5 million carbon-enhanced metal-poor (CEMP) stars for future exploration of the chemo-dynamical properties of CEMP-no and CEMP-s stars in the halo and disk systems of the Galaxy.

The Dark Energy Spectroscopic Instrument (DESI) collaboration is conducting a five-year redshift survey of 40 million extra-galactic sources over 14,000 square degrees of the northern sky up to the redshift of 4 with the Mayall 4-meter telescope at Kitt Peak National Laboratory. One of its primary goals is to measure the cosmic expansion history precisely and accurately through the measurements of baryon acoustic oscillations (BAO). In this talk, I will present the analysis of the DESI First Year Baryon Acoustic Oscillations using the distributions of galaxies and quasars over the redshift range of 0.1-2, the estimates of the relevant systematics, and their intriguing cosmological implications, including the time-evolving dark energy.

Previously, offsets between galaxies and mass during cluster collisions were regarded as a promising indicator for evaluating the self-interaction cross-section of dark matter. However, past investigations based on these offsets have been hindered by significant biases regarding the phase and geometry of the merger. I will introduce a reliable constraint on the self-interaction of dark matter using a novel and effective approach with observations of cluster collisions featuring double radio relics. By utilizing the distance between relics relative to the distance between halos as a gauge for dark matter characteristics, we have established an upper limit of 0.33 cm^2 g^-1 for the self-interaction cross-section with 68% confidence. This marks the first robust outcome derived from colliding clusters, accounting for ambiguities such as mass variability, viewing angle, collision velocity, merger phase, impact parameter, and gas slope.

Photons looping around photon shells in black hole spacetimes form a sequence of higher order images -- the photon ring. Unlike in the case of the direct image, the size and shape of the photon ring reflects properties of spacetime, aka "clean geometry" with only limited impact of the configuration of the emitting source, aka "dirty astrophysics". Thus, they enable unprecedented robust observational tests of strong gravity, possibly including estimates of black hole spin, or constraining deviations from the Kerr metric. For at least 1 black hole in the Universe, M87*, the photon ring can be characterized with space radiointeferometry at mm wavelengths. I will talk about the ongoing plans and efforts to do it in the next decade with the

proposed NASA Black Hole EXplorer (BHEX) space VLBI mission.

Interferometer have already been commercialized and utilized in various fields, but it is too weeak to enviromental condition, its performance remains significantly limited. Therefore, research continues to apply advanced measurement techniques in various fields, such as optical measurement technology for gravitational wave detectors and large-aperture optical measurement technology. In this talk, I will introduce about birefringence sensor for test mass of gravitational wave detector and interferometric sensor for lareg-scale optics. In addition scattered light analysis from large scale optics will be introduced. 

본 세미나에서는 달 탐사를 위한 인공지능 기반 3차원 컴퓨터 비전 융합 기술을 소개합니다. 먼저, 연구실에서 수행해온 자율주행을 위한 3차원 시각인지 기법에 대한 대표 연구 성과를 살펴보고, 최신 인공지능 기법과 3차원 구조 복원 및 모델링 기술의 동향을 소개합니다. 이러한 기술들을 활용하여 달 궤도선 탑재체로 촬영한 영상을 통해 달의 3차원 지형을 복원하는 방법을 소개합니다. 특히, 기존 인공지능 및 컴퓨터 비전 분야의 태스크와 달 탐사를 위한 태스크의 차이점과 도전 과제를 분석하고, 이를 극복하기 위한 방안을 공유합니다. 이를 통해 인공지능과 컴퓨터 비전 기술이 달 탐사에 어떻게 혁신적인 변화를 가져올 수 있는지 논의하고자 합니다.

Planetary soft landing is a critical challenge in space exploration, requiring precision and robustness to ensure the safety and success of lander missions. Convex programming, known for its global optimality and computational efficiency, offers significant advantages for designing landing trajectories and control strategies under complex constraints and uncertainties. In this presentation, we explore the application of convex programming to develop algorithms for soft landing on planetary surfaces. We introduce our approaches that utilize first-order methods and distributed optimization to enhance computational speed and scalability. The first-order methods are particularly advantageous as they are simpler and can be efficiently implemented on Graphics Processing Units (GPUs), leveraging their parallel processing capabilities to handle large-scale problems more effectively. Furthermore, we discuss the use of various testbeds, including indoor flight test facilities and rocket test beds, which play a pivotal role in validating our proposed algorithms and ensuring their reliability and effectiveness in real-world scenarios. This talk highlights how cutting-edge optimization techniques, combined with advanced computational resources and rigorous testing, pave the way for safer and more efficient planetary landings.

Barred galaxies are a common type of galaxies in the local universe, observed in over 60% of disk galaxies. The bar structure plays a significant role in determining galaxy substructures such as spiral arms, rings and central dust structures. It is also a crucial driver of the secular evolution of galaxies, redistributing the mass of gas, stars, and even dark matter: it drives gas into the central regions of galaxies, builds a pseudo- or boxy/peanut bulge, and can even elongate the dark matter halo. According to theoretical studies, in an isolated system, a bar structure rapidly forms when a stellar disk is unstable and grows by interacting with the dark matter halo. However, observations do not find evidence for the growth of bar structures in terms of their length, strength, and pattern speed, which induces tension between the distribution of dark matter in simulations and observations. Furthermore, galaxy interactions that induce barred galaxies add complexity to our understanding of barred galaxies. In this talk, I will introduce our recent and ongoing work on barred galaxies using photometry from SDSS, PS1, HST, DESI, and CFHT and spectroscopy from Gemini, CALIFA, MUSE, and JWST. Our work spans the methods to detect barred galaxies to their evolution in the context of their main properties: length, strength, and pattern speed. Lastly, I will introduce the important role of the KASI’s next projects, including K-DRIFT, LSST, and the DARWIN project, in the study of barred galaxies.

SiCfiller/SiC ceramic composites were prepared using a SiC powder and a liquid polycarbosiane (PCS) ceramic precursor. Ultra-fine SiC powder (d50: 170nm), prepared by mechanical alloying process, was used to prepare aqueous SiC slurries with the solid loading of 66 - 70 vol%. By the optimization of dispersion condition and the oxidation treatment of the SiC powder, SiC slurry up to 70 vol% solid loading was successfully prepared. The maximum green density of SiC compact after drying the slurry was 78%. Precursor-impregnation & pyrolysis process (PIP) was performed using SMP-10 liquid PCS precursor. The weight of the SiC composites increased almost linearly up to 4 PIP cycles and the mass gain became less efficient afterwards. The 4-point flexural strength of the SiC composites were 204 and 265MPa at 25 and 2,000℃, respectively under argon atmosphere. The result clearly indicates the excvellent thermal stability of the SiC cpmposites fabricated using the PCS precursor.

When you look at the sky on a clear night, you probably enjoy the twinkling of stars. However, if you are an astronomer, you might find it extremely annoying. Almost as soon as telescopes were invented, astronomers realized that the quality of images was limited by atmospheric turbulence, which distorts short exposure and blurs long exposure astronomical images. Even if we have 8-10 meter class telescopes now, without AO, the telescope's angular resolution would be limited by the atmospheric turbulence “seeing” -the size of the blurred image is almost two orders of magnitude worse than what the telescopes could achieve. To overcome this limitation, the first concept of adaptive optics (AO) was proposed by H. W. Babcock in 1953 for ground-based telescopes. However, the technology for AO components was not mature enough then. From the late-1980s, astronomers became interested in applying the AO technique to astronomy. As of today, AO has rapidly been developed over the past 70 years and has become a state-of-the-art technique. The wavefront aberration induced by atmospheric turbulence can be measured by a wavefront sensor and compensated for by a wavefront corrector, thereby deblurring the images in part or entirely. This presentation introduces astronomical science that can be achieved with modern AO technologies. We also present recent technology trends for the AO system, such as types of wavefront sensors (WFSs) and wavefront correctors. In the wavefront sensors section, we present Shack-Hartmann WFS, pyramid WFS, and curvature WFS. In the wavefront corrector section, we introduce wavefront correctors such as deformable mirrors and a spatial liquid modulator. Lastly, we introduce modern AO systems with multiple laser and nature guide stars for various applications.

Understanding ice composition is crucial in star and planet formation. To investigate ices in young stellar objects (YSOs), we can utilize ALMA, JWST, and the upcoming SPHEREx mission. ALMA observations reveal sublimated complex organic molecules, while JWST provides detailed ice absorption spectra. SPHEREx will perform all-sky ice mapping. We emphasize burst accretion, where episodic increases in accretion rates cause ices to sublimate, revealing their composition. YSOs gain mass through episodic accretion, causing luminosity variability. Catching burst events by monitoring YSOs allows for detailed ice composition studies. Identifying bursting YSOs at different evolutionary stages will enable us to track ice evolution from early star formation to planet formation, enhancing our understanding of surface chemistry.

Observations reveal the organization of the interstellar medium into filament networks. In molecular clouds, the densest filaments are identified as the precise birthplaces of solar-mass stars, while high-mass stars form in the hubs where the filaments merge. To understand the formation process of star-clusters, it is thus essential to describe the formation and evolution of filaments and hubs and their fragmentation into pre-stellar cores, the progenitor of stars. I will present theoretical and observational studies indicating the formation of filamentary molecular clouds at the edge of expanding bubbles. I will then show observational results suggesting the role of filament coalescence and hub-filament systems in the formation process of stars from low to high masses. I will also discuss our new study proposing the formation of the Sun along a dense molecular filament. We suggest that the host filament may play an important role in shielding the young solar system from a nearby supernova explosion while intercepting the required amount of supernova ejecta to explain the observations of primitive material found in meteorites. 

The dark energy equation of state parameter w is measured with sufficient accuracy to discover that w must be larger than one in the flat CDM universes, namely dark energy is not the cosmological constant. A series of large-volume galaxy redshift surveys samples up to redshift ~0.8 produced by the Sloan Digital Sky Survey are used in the analysis, and the expansion history of the universe was measured using an extended version of the Alcock-Paczynski test (Park et al. 2019). The test exploits the fundamental fact that gravity is an isotropic force and the statistical pattern of galaxy clustering can be used as a standard shape that is conserved with time. The new analysis of the SDSS data indicates that the expansion of the universe is indeed accelerating but the acceleration is a little slower than expected in the flat LCDM universe. The dark energy equation of state parameter is measured to be w = −0.903±0.023, a 4.2σ deviation from −1! This finding of a new "w tension" inevitably leads us to discard the cosmological constant as the source for the accelerated expansion and consider alternative quintessence models. We are now making a more accurate measurement of w using the upcoming DESI survey data to test if w is constant or evolving.

The atmospheres of planetary objects contain natural dust particles, and planetary scientists call them aerosols or haze particles. The chemical and physical properties of the haze particles in the atmospheres of Jupiter, Saturn, and Titan have been revealed by Cassini and Juno: the Saturn and Jupiter space missions, respectively. Cassini arrived at the Saturnian system in 2006, and Juno at the Jovian system in 2016. We analyzed infrared spectra from these missions in order to extract haze spectra from raw spectra, which are heavily entangled by molecular lines, especially by strong CH4 emission and absorption lines. We first analyzed the 3.0-3.5 and 2.0-2.5 mm spectra of Titan observed by Cassini/VIMS, a near-IR camera and spectrometer. Surprisingly, we found that the haze spectra of Titan are very different from the typical spectra of ‘tholins’, which have been laboratory-made and claimed by Carl Sagan for the haze particles in the atmospheres of Titan, Saturn, and Jupiter for more than 40 years. The derived haze spectra of Titan are, instead, very similar to the typical spectra of aromatic hydrocarbons at high altitudes and aliphatic hydrocarbons at low altitudes. The tholins were even considered to be one of the important components of interstellar dust particles. We also analyzed the Cassini/VIMS 3.0-3.5 mm spectra of Saturn to extract Saturnian haze spectra. We found that the polar haze is dominated by aromatic hydrocarbons while the haze at lower latitudes mostly consists of aliphatic hydrocarbons. This spectral variation in the di?erent latitudinal regions suggests that newly created haze particles at the high altitudes in the auroral regions of Saturn undergo an aging process mainly during latitudinal advection/di?usion from the polar atmosphere to the low altitude and low latitudinal regions, while in the atmosphere of Titan, the aging process mainly occurs during the vertical precipitation process of haze. Recently, we analyzed the 2.0-2.5 mm spectra of Jupiter’s polar regions observed by Juno/JIRAM, another camera and spectrometer very similar to Cassini/VIMS. We were able to extract the haze spectra of the polar regions of Jupiter; and found that the spectra are roughly similar to those of Titan suggesting similar chemical and physical processes of haze particles in the atmosphere of Jupiter.