Very long baseline radio interferometry (VLBI) with ground-based observatories is limited by the size of Earth, the geographic distribution of antennas, and the transparency of the atmosphere. In this whitepaper, we present Capella, a tentative design of a space-only VLBI system. Using four small (<500 kg) satellites in two orthogonal polar low-Earth orbit planes, and single-band heterodyne receivers operating at frequencies around 690 GHz, the interferometer is able to achieve angular resolutions of approximately 7 microarcsec. Within a total observing time of three days, a near-complete uv plane coverage can be reached. All key components required for Capella - radio telescope, receiver, sampler, recorder, atomic frequency standard, positioning system, data downlink, and pointing control system - are already available, some of them off-the-shelf; the science payload of each satellite has a mass of about 230 kg and consumes about 550 W of power. The data from the telescopes can be correlated on the ground using dedicated versions of existing Fourier transform (FX) software correlators; in addition to the steps required by VLBI data correlation and calibration in general, dedicated routines will be needed to handle the effects of orbital motion, including relativistic corrections. With the specifications assumed in this whitepaper, Capella will be able to address a range of science cases, including: photon rings around supermassive black holes; the acceleration and collimation zones of plasma jets emitted from the vicinity of supermassive black holes; the chemical composition of accretion flows into active galactic nuclei through observations of molecular absorption lines; mapping supermassive binary black holes; the magnetic activity of stars; and nova eruptions of symbiotic binary stars - and, like any substantially new observing technique, has the potential for unexpected discoveries. 

New observational methods often trigger new discoveries in astronomy. To explore the universe in an innovative way, we are constructing a multiple telescope, the 7-dimensional telescope (7DT) in Chile. 7DT is made of twenty, 0.5-m diameter wide-field telescope, and the first ten units started the operation in October, 2023, with the expected completion of the full system in 2024. With 7DT, we will perform the 7-dimensional sky survey (7DS), a wide-field, time series, spectral mapping of the southern sky. The survey aims to (i) understand the spectral variability of astronomical sources through time-series spectral mapping such as active galactic nuclei; (ii) provide a spectral map of the sky that can be used to study spatially resolved stellar population of galaxies, cosmology, etc; and (iii) rapidly identify electromagnetic counterparts of gravitational-wave sources for successful multi-messenger astronomy. In this talk, we will introduce 7DT and 7DS and outline the unsolved problems that 7DS will tackle. We will also early images and the data taken with 7DT as well as its current performance, which demonstrate the scientific promises of 7DS. We will also briefly discuss the synergies between 7DT and KASI’s initiatives such as SPHEREx, KMTNet, and the Vera Rubin Observatory.

Gaia DR3 provides state-of-art data of proper motions (transverse velocities), parallaxes (distances), radial velocities, and luminosities for nearby stars. Statistical analyses of binary stars show that Newton-Einstein standard gravity holds for the orbit size less than about 1000 astronomical units (au) or the internal acceleration greater than about 6 nanometer per second squared. However, binary orbital motions exhibit a gradual systematic anomaly from 1000 to 5000 au and a pseudo-Newtonian gravity with Newton’s constant boosted by a factor of 1.4 holds for > 5000 au. Remarkably, this behavior agrees with the prediction of Milgromian (modified Newtonian dynamics) gravity. Consistent results are obtained from three independent methods of statistical analysis, the ``acceleration plane analysis”, the “normalized velocity profile analysis”, and the “stacked velocity profile analysis” based on various samples of binaries. These results indicate that general relativity breaks down in the low acceleration limit because its nonrelativistic limit becomes Newtonian. A paradigm shift is under way in astrophysics, cosmology, and theoretical physics. Implications of the results and future prospect are discussed.

지난 40년간 방위산업 전문기업으로 대한민국 자주국방에 기여해온 한화시스템의 사업영역인 우주영역 인식 분야에 대한 기술개발 현황 중 우주감시시스템의 운용목적, 우주감시시스템의 개발현황, 우주방호 레이저에 대한 개발 현황을 소개합니다.

소형발사체 스타트업 페리지의 Blue Whale 1 발사체 개발 현황과 발사 계획을 소개하며, 이를 응용한 독특한 우주관측 임무를 제안한다.

뉴스페이스 시대의 우주산업 시장과 한국의 우주 감시를 포함한 우주산업 전략을 고찰하고, LIG넥스원의 위성 분야의 사업현황과 계획을 소개하며, 천문연과의 협업분야를 제안함.

Comparisons of quiescent galaxies in the distant universe with their counterparts in the local volume show that the structure of galaxies continues to change well after they stop forming stars. Very compact galaxies, that have the stellar mass of the Milky Way and the size of the Milky Way bulge, seem to disappear between redshifts z~2 and z~0. The average size of quiescent population increases by a factor of a few over the same redshift interval. In contrast to the existing surveys of high-redshift universe, at intermediate redshift (0.2 < z < 1) we trace quiescent population by combining high-resolution imaging and dense redshift surveys that map large areas of the sky. We utilize these spectro-photometric datasets as a missing link that completes the picture of galaxy size growth in the quiescent phase. I will describe how information-rich surveys of the universe at intermediate redshift enable us to test models of galaxy mass assembly by accurately characterizing the correlations between structural evolution of galaxies, their stellar population properties, and the environment they inhabit.

Polarimetry is established as the third eye of humankind into the Universe, complementing photometry and spectroscopy. Dust and magnetic fields are ubiquitous the Universe and widely thought to play crucial roles in many astrophysical processes, from star formation and stellar feedback to planet formation, molecule formation, and life. Polarization of light induced by alignment of dust grains with magnetic fields is a leading tool for illuminating the dusty and magnetized universe from the UV-optical-NIR to far-IR and (sub-)mm wavelengths. The most powerful observatories (ALMA, NOEMA, IRAM/Nika2-Pol, SOFIA/HAWC+, JCMT/Pol2, APEX/A-mKID, TolTec, BLASTPOL) are providing a vast amount of polarization data, which promise to shed light on the fundamental dust physics (e.g., grain alignment and rotational disruption) as well as the key role of dust and magnetic fields in many astrophysical processes. In this talk, I will comprehensively review the current state-of-the-art of our theoretical frameworks, computational tools, and observational constraints of dust physics and magnetic field properties using multi-wavelength polarization data. I will then introduce a new technique for probing 3D magnetic fields using dust polarization and our grain alignment theory.

Here I would like to introduce the NRF project “A study on the evolutionary process of late-type stars through maser observations” (called SMASTES: Simultaneous Multi-mAser Survey Toward Evolved Stars) which has been starting since Sept. 2022 with a three year plan. SMASTES aims to study statistically characteristics of SiO and H2O maser properties in ~150 M-type oxygen-rich AGB, ~150 S-type AGB and ~150 post-AGB stars according to evolutionary stage using the upgraded wide four-band receiving system of the KVN. In addition to the existing main observation lines of 22 GHz H2O and 43/42/86/129 GHz (v = 1, 2, J = 1-0; v = 1, J = 2-1, J = 3-2) SiO masers, the SiO v = 3, J = 1-0; v = 2, J = 2-1, 3-2; 28SiO v = 0, J = 1-0, 2-1, 3-2; 29SiO v = 0, J = 1-0, 2-1; 30SiO v = 0, J = 1-0 lines are further observed simultaneously together with CS, HCN, SiS, SO, and SO2 thermal lines. Observations toward ~155 oxygen-rich AGB stars (SMASTES I) were completed between Feb. and June 2023. For observational studies on ~155 S-type stars (SMASTES II), the observations are being carried out by the KVN 2023B proposal since September of this year. The observational proposal for ~150 post-AGB stars (SMASTES III) was submitted for the KVN 2024A season. Through these observations, the characteristics of maser properties, chemical trends associated with characteristics of maser properties, SiO abundance and dust formation etc. will be explored according to the oxygen-rich AGB, S-type AGB, and post-AGB phases. A kinematic acceleration of mass loss and asymmetric outflows from the central star to atmosphere → dust layer → outer circumstellar envelope are also investigated during the evolution of early AGB, thermal pulse late AGB, and post-AGB stars. In particular, observational studies on S-type AGB stars with C/O≈1 as a transitional phase from oxygen-rich to carbon-rich stars and post-AGB stars as a transitional phase from AGB stars to planetary nebulae, which have not been studied much so far, will be focused.

As the frequency of electromagnetic waves becomes lower, the signal can penetrate deeper into the sea, while the installation and operation costs get higher. That is why only some of the developed countries operate Very-Low-Frequency (VLF) transmitters that can be used for sending electromagnetic signals to submersible vehicles. This talk will give a brief introduction to the effects of VLF transmitter signals on ionospheric cold plasma and energetic particles coming from the magnetosphere. We also review the signatures captured by Korean satellites, such as NextSat-1. Finally, we discuss the possible contribution of the recently launched SNIPE fleet to this topic.

The ESA mission Gaia is regularly scanning the sky since 2014.5 down to magnitude V≈20.7, and its 4th harvest has just been published with the recent Gaia Focus Product Release. I will first give a brief review of the Gaia mission, its status, observations, instruments and data releases. Next, we will see some of the scientific results obtained for asteroids, focusing on astrometry and photometry. We will expose in particular the improvement on asteroid orbital solutions obtained within the FPR. Last, we will touch upon synergy with ground-based observations, and promises for the study on the dynamics of Solar System Objects.

galactic nuclei are extreme environments where stars are densely packed around a supermassive black hole (SMBH). Occasionally, dynamical interactions in the galactic center lead the stars to interact violently at short distances with each other or with the SMBH, resulting in the formation of nuclear transients. In this talk, I will discuss two types of nuclear transients, tidal disruption events and high-velocity collisions between stars, based on the results of detailed hydrodynamics simulations. Tidal disruption events are one of the most dramatic nuclear transients in which a star is tidally disrupted by the SMBH in a few hours. The conventional picture has been that a star is fully disrupted at the first pericenter passage and the debris circularizes rapidly. However, these events are in fact more diverse and they can be categorized into several groups with different observational signatures depending on stellar pericenter distance, from partial disruptions (i.e., partial mass loss and surviving remnant) to full disruptions which is further sub-categorized depending on relativistic effects. On the other hand, disruptive collisions are the events where two stars collide at a very high relative velocity near the central SMBH. The collision product, a homologously expanding gas cloud, can generate a flare as bright as tidal disruption events. Subsequently, the expanding gas cloud would interact with the nearby SMBH, generating a second, possibly even brighter accretion-driven flare. Because these can happen near BHs at any mass scale, if the accretion is efficient, these disruptive collisions could contribute to the growth of black holes.

A GPU (Graphic Processing Unit) spectrometer for the ALMA (Atacama Large Millimeter/submillimeter Array) Total Power Array has been developed by the KASI and the NAOJ (National Astronomy Observatory of Japan).  It is a first in-kind contribution of the KASI to the ALMA international collaboration.  The development project went through a series of milestones, from a concept design review in 2016 to commission and science verification in 2023.    During the ALMA maintenance period of February 2022, the GPU spectrometer was installed in a technical building at the Array Operation Site by its developers from  the KASI and the NAOJ.   Right after the installation, SiO (J=2-1; v=1) 86 GHz maser spectral lines toward the Orion KL region were successfully detected using the spectrometer.   The spectrometer will be used from the ALMA Cycle 10 (October 2023) for science observations.

We are now living in the era of the 4th industrial revolution, and we would like to introduce artificial intelligence and mobility (autonomous driving), which are representative technology trends. Artificial intelligence is a collection of rapidly developing digital data and machine learning based on big data, and now deep learning technology is becoming common. In addition, with the commercialization of various means of transportation, such as the Tashu bicycle, quick board, and unmanned vehicles, research on laws, systems, and technologies for future mobile devices is very active. We would like to introduce ETRI's research trends on mobility technology (autonomous driving) required for transportation.

With the recent successful launch of the Nuri, Korea has become a country with world-class space development technology. In addition, the so-called New Space era in which private operators also launch rockets has opened. Metaspace, an astronomy company, is also making various efforts in line with the rapidly changing era. We will introduce what we have been working on and what we will do in the future.

Galaxy clusters are important probes in the study of galaxy formation and cosmology. Dense spectroscopy is a unique tool for investigating cluster properties and their galaxies. In this talk, I will highlight the diverse applications of dense spectroscopy, including the derivation of velocity dispersion functions and the novel technique of spectroscopic weak lensing tomography. These approaches will be important tools for future large-scale spectroscopic surveys.

The next-generation survey observations for cosmological studies, such as Rubin and Euclid, are expected to start observation this year. To reveal the mystery of dark energy and dark matter in the Universe, these surveys will bring us unprecedented constraining power on cosmological parameters and ample opportunities to test beyond the standard cosmological model (LCDM). To understand where we are standing with the most recent observations, in my talk, I will overview the weak lensing analysis results of current surveys as well as the challenges, including the baryonic feedback effect. As a main builder of the Kilo-Degree Survey (KiDS), the current European Survey team, I will also introduce upcoming updates on the last release of the KiDS (KiDS Legacy) data, whose scientific results are scheduled to be announced this Autumn.

I'll present a novel method of probing dark-matter properties by using the mass spectrum of gravitational-wave sources.

Asteroids are considered to be among the most primitive celestial bodies in our solar system and are crucial for understanding the origin and formation processes of the solar system. Furthermore, the significance of asteroids has been increasingly recognized, both in terms of planetary defense and possible space resource utilization. Astronomical observations have been one of the most powerful methods to investigate the physical properties of asteroids, enabling us to obtain information such as orbit, size, shape, spin state, and surface properties. In this talk, I will introduce an overview of how astronomical observations have been used to study the physical properties of asteroids. Specifically, I will present the outcomes of large-scale survey observations and discuss the synergistic effects of utilizing the observation results from various surveys. Additionally, I will present the interplay between space missions and astronomical observations in asteroid research, highlighting their complementary roles and the unique benefits each approach provides.

The nearby radio galaxy M87 is a prime target to study black hole accretion and jet formation. Event Horizon Telescope observations of M87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure which was interpreted as gravitationally lensed emission around a central black hole. Here we report new images of M87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. High resolution imaging reveals a ring-like structure of 8.4-1.1+0.5 Schwarzschild radii in diameter, ~50% larger than that seen at 1.3 mm, with the outer edge at 3.5 mm also being larger than that at 1.3 mm. This larger and thicker ring indicates a significant contribution from the accretion flow with high self-absorption opacity effects, added to the gravitationally lensed ring-like emission. The new images show that the edge–brightened jet connects to the black hole’s accretion flow. Close to the black hole, the emission profile of the jet launching region is wider than the expected profile of a black hole driven jet, suggesting the possible presence of a wind associated with the accretion flow. A paper summarizing these findings has been published in the journal Nature. During this presentation, I will discuss the physical significance of the M87 black hole images captured at 1.3 and 3.5 mm, as well as the experiments underway in Korea that aim to provide further insight into the characteristics of this black hole.

Understanding galaxy evolution is one of the big subjects in modern astronomy. Galaxy clusters and superclusters, which sit on the top of the hierarchy of structure formation in the universe, are valuable objects to witness various types of galaxies and environments and study how the properties of galaxies change with their surroundings. Submm galaxies (SMGs) are holding hints to reveal the mystery of star formation history in the early universe. In this talk, I will introduce the study of galaxy evolution in the galaxy clusters with the large-scale structure environment in the SA22 field. From this study, we checked the `web feeding model,’ which is that more linked (with their environment) galaxy clusters have less quenched population by investigating the correlation between properties of confirmed galaxy clusters and the large-scale structure environment. Second, I will present the newly found submm galaxies(SMGs) with JCMT SCUBA-2, star-forming populations having the key to revealing the hidden star formation in the universe, in the JWST Time Domain Field near the north ecliptic pole. I also introduce the preliminary image of the JWST for these submm galaxies.

Currently, the Moon has dispersed crustal magnetic anomalies instead of a global magnetic field like the Earth. The magnetization of the lunar crust has been studied for many years using magnetometer data obtained on the lunar surface, orbiting spacecraft, and lunar samples returned during the Apollo missions. Recent missions with polar orbits, such as Lunar Prospector and Kaguya, have expanded these measurements globally. Despite knowing that the lunar crust is magnetized since the Apollo era, we still lack a complete understanding of how crustal magnetism was generated. Additionally, due to the absence of a global magnetic field and atmosphere, solar wind particles directly impact the lunar surface, leading to a different solar wind interaction with the Moon compared to Earth. The wave activities generated by solar wind interaction with the Moon have been studied for many years. However, we still do not completely understand how and where they are generated. In this talk, I will present the magnetic anomalies on the Moon and the source model of lunar magnetic anomaly. I will also present ultra-low frequency (ULF) waves generated by solar wind interaction with the Moon and the generation mechanism of the observed lunar waves.

AGB stars are very important in stellar evolution. The death of most stars with 1-8 solar mass is a result of heavy mass loss in this phase. After losing the stellar envelope, they evolve to post-AGB stars with higher temperature at almost constant luminosity. In observations, the gas envelope evolves to asymmetry structures and massive material is suddenly ejected by bipolar or multipolar outflows. These objects are classified as pre-planetary nebulae (or PPN) because it takes only a few hundred years evolving into the planetary nebula phase, leaving a white dwarf and ionized gas envelope in space. When we look into the sky, there are various shapes of the planetary nebulae. Studying the properties of outflows can help us to understand the complex physics and chemistry in the planetary nebulae. I’ll present recent research on three of our targets, CRL 618, Cotton Candy Nebula, and V Hydrae, possessing multi-directional and multi-epoch outflows. We explore a possible scenario where the mass loss of AGB stars could be periodically accreted by a companion passing of the periastron in a high-eccentricity orbit, forming disks and multipolar outflows.

Planets form in protoplanetary disks around young stars. As most young stars form in cluster environments, planet forming disks are exposed to various levels of external UV radiation. Such external UV radiation plays an important role in protoplanetary disk evolution affecting disk lifetime, disk properties, and planet formation. Photoevpaorating protoplanetary disks (proplyds) are found near O stars in the Orion Nebula Cluster (ONC), which harbors over hundreds of them. We have identified more proplyds around two other young star forming regions in Orion A and B clouds: NGC 1977 and NGC 2024. Proplyds are found mostly in Orion in vicinity of O stars (ONC), but as low as B1V star (NGC 1977) providing diverse ranges of UV environments. In this talk, I will present recent work on properties of Trapezium cluster at the heart of Orion Nebula, and discovery of proplyds in NGC 1977 and NGC 2024. These clusters provide excellent laboratory to study interplay between UV radiation from massive stars and protplanetary disks in strong (ONC, NGC 2024) and intermediate (NGC 1977) UV radiation environments. NGC 2024 is unique as it provides the youngest age among the three regions (age <0.5-1 Myr), while NGC 1977 provides the weakest UV environment where proplyds are discovered. I will also present our kinematic studies of the proplyds and non-proplyd young stars in ONC and NGC 1977, and explore possible explanations for "proplyd life time problem".

Previous simulation studies suggest that dust-obscured AGNs appear for a certain period when merger-driven star-forming galaxies evolve to unobscured AGNs. The dust-obscured AGNs would have red colors due to the dust extinction from their host galaxies, and they are expected to have enhanced black hole activities than unobscured AGNs. Red AGNs have very red colors, and they have been suspected as the intermediate-stage, dusty AGNs. However, it is not yet clear if red AGNs really correspond to the dusty young AGNs due to a lack of intrinsic properties of red AGNs. For unveiling the intrinsic properties of red AGNs, we study unobscured and red AGNs. There are three main themes: (i) derivation of new black hole mass estimators that can be used for red AGN study; (ii) investigation of red AGN selection methods to test its usefulness to identify dusty red AGNs; and (iii) investigation of the accretion rates of red AGNs to see if they have the properties as predicted in the simulation studies.

본 발표는 “우주법의 구조와 미래”(The Structure and Future of Space Law)에 관한 것으로 1957년 10월 4일 소련의 스푸트니크(Sputnik) 1호 발사로 우주활동이 본격적으로 전개되어 가자 이를 규제하기 위한 우주법이 탄생하면서 1967년 우주조약(Outer Space Treaty)을 비롯한 1968년 구조협정(Rescue Agreement), 1972년 책임협약(Liability Convention), 1975년 등록협약(Registration Convention), 1979년 달협정(Moon Agreement) 등 우주관련조약들과 관습법(customary law) 및 연성법(soft law)의 의미를 살펴볼 것이다. 최근 미국이 1970년대 아폴로 프로젝트 이후 50 여년 만에 달에 우주인을 보내기 위한 유인 달탐사 프로그램인 ‘아르테미스 프로그램’을 진행하면서 수립한 현재 미국을 비롯한 23개국이 동참하고 있는 ‘아르테미스 약정’(Artemis Accords)은 기존 우주법과 어떠한 관련을 가지고 있는가 하는 문제도 살펴볼 것이다. 마지막으로 우주법의 미래는 어떻게 전개될 것인가 하는 문제를 살펴볼 것이다.

The talk discusses about the current development activities of a small satellite launch vehicle mostly by the domestic startup, Perigee Aerospace Inc.

달, 화성, 소행성 등에 대한 우주탐사는 이제 하나의 산업이자 경제가 되고 있다. 다른 영역에서의 경제학과 마찬가지로 우주탐사 경제학에서도 핵심은 바로 비용과 수익이다. 이 콜로퀴엄에서는 우주탐사에 드는 각종 비용들과, 수익 창출이 가능한 달, 화성, 소행성 자원들에 대해 알아본다. 구체적으로는 로켓 재사용으로 인한 발사비용 절감의 비밀, 달에서 채굴한 얼음을 지구 궤도에서 로켓 연료로 파는 사업 모델, 월면에서 채굴하는 He-3의 진짜 가치, 우주 엘리베이터의 실현 가능성, 다누리호가 선택한 WSB/BLT 궤도의 작동 원리 등에 대해 논의한다.

딥러닝은 최근 기상 및 기후 분야에서 다양한 문제를 해결하기 위한 방법론으로 활용되고 있습니다. 지금까지 기상 분야의 미래 예측은 물리 또는 통계 모델에 기반한 방법론이 활용되었으나, 딥러닝 기반 시계열 영상 예측 기술의 발달로 데이터로부터 학습을 통한 시계열 예측 가능성이 여러 연구를 통해 확인되고 있습니다. SIA에서도 기상위성 영상을 활용한 시계열 예측 모델 개발 연구를 수행하고 있습니다. 본 콜로퀴움에서는 SIA에서 개발하고 적용한 두 가지 시계열 예측 모델에 대해 소개하고자 합니다. 첫번째는 2022년 기준으로 가장 성능이 좋은 시계열 영상 예측 모델인 CrevNet을 기상 위성 영상에 적용하여 집중호우 및 위험기상 감시에 중요한 대류셀의 발달과 이동을 예측하고 트래킹할 수 있는 모델입니다. 두번째는 시계열 영상의 시간 고해상화를 위해 개발된 Flow-based 모델로 시간 고해상화를 위해 중간 영상을 생성할 수 있으며, 같은 방법으로 외삽을 수행하여 미래 영상도 생성할 수 있도록 하였습니다. 이번 콜로퀴움 발표에서 두 모델의 미래 예측 결과를 통해 각 모델의 한계점 및 고도화 방안에 대해 논의하고자 합니다.

The high-mass protostar G358-MM1 underwent an accretion burst in 2019. Such events are rare, and essential to observe in order to test and refine theories of high-mass star formation. During the accretion burst six VLBI observations were made of the 6.7 GHz methanol maser in G358-MM1. The observations traced a 'heat-wave' of accretion energy as it moved through the disk. In this talk I will report the results of the VLBI monitoring campaign and introduce a new, and accidentally discovered, technique called 'heat-wave mapping' which used the accretion burst and multi-epoch VLBI observations to map the spatio-kinematics of the accretion disk at milliarcsecond resolution.