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.

Solar Energetic Particles (SEPs) are composed of protons, electrons, and heavy ions with energies ranging from hundreds of keV to MeV. They are accelerated in magnetic reconnection regions (impulsive events) and by Coronal Mass Ejection (CME)-driven shocks (gradual events). Large-scale SEP events are one of the most important phenomena in terms of space weather. They pose a risk of radiation exposure to humans and equipment in space. In this presentation, I will show the study of the large SEP sources using extreme-ultraviolet (EUV) images and Potential Field Source Surface (PFSS) extrapolations from the conventional magnetograms and AI-HMI magnetogram on a near real-time basis. The features of SEPs strongly depend on physical quantities of CMEs and flares at the connecting footpoints between the sources and the spacecraft. I will present the temporal and spatial variations of SEP fluxes observed by in-situ measurements and the relations between the fluxes and the quantities of the SEP sources.

Dwarf novae are a binary system with short orbital periods (a few minutes to hours). Being one of the cataclysmic variable stars, dwarf novae show quasi-periodic outbursts which are triggered in the accretion disk around the primary star via accreting materials from the secondary star. During outbursts, they show various peculiar shapes of the observed light curves. For the past ~70 years, over five thousand dwarf novae have been observed and outburst mechanisms became well known. Thermal-viscous instability makes accumulated mass in the accretion disk dumped onto the primary star during the outburst and the accretion disk become brightened. Despite the many previous studies, some parts of the evolution of dwarf novae are still unknown since, especially, dwarf novae with very short orbital periods of <60 minutes or low-metallicity secondary stars are rarely observed. KMTNet has the ability to discover these rare dwarf novae and in this talk, I will show the strength of the KMTNet in finding these invaluable pieces to get better understanding of their evolution.

There have been attempts to probe a wide range of dark matter candidates, whose mass ranges from 10^{-22} eV to the Planck scale (and beyond Planck scale if they are not particles). After presenting a brief history of dark matter search, I will discuss the dark matter parameter space allowed by the current observation data. I will then illustrate a few popular DM examples including axion-like particles (ALPs), Weakly Interacting Massive Particles (WIMPs), Primordial Black Holes (PBHs) along with the search efforts for those compelling dark matter candidates.

The evolution of the gravitational potentials on large scales due to the accelerated expansion of the Universe is an important and independent probe of dark energy, known as the integrated Sachs-Wolfe (ISW) effect. We measure this ISW effect through cross-correlating the cosmic microwave background maps from the Planck satellite with a radio continuum galaxy distribution map from the recent Rapid ASKAP Continuum Survey (RACS). We detect a positive cross-correlation at ~2.8σ relative to the null hypothesis of no correlation. We parameterise the strength of the ISW effect through an amplitude parameter and find the constraints to be A_ISW = 0.94^{+0.42}_{-0.41}, which is consistent with the prediction of an accelerating universe within the current concordance cosmological model, ΛCDM. The credible interval on this parameter is independent of the different bias models and redshift distributions that were considered when marginalising over the nuisance parameters. We also detect a power excess in the galaxy auto-correlation angular power spectrum on large scales (ℓ≤40), and investigate possible systematic causes.

Galaxies are known to change dramatically over cosmic time in terms of their star formation, masses, structure, and internal (chemical) properties. While single-wavelength studies in pencil-beam areas on sky provide some insights, multi-wavelength studies of the full galaxy population are crucial to understand galaxy evolution as a whole. In this talk, I present different aspects of galaxy evolution and the latest (and future) surveys that enable us to study them. The ALPINE survey with ALMA is one of the largest of such multi-wavelength surveys, combining UV to sub-mm observations of z=4-6 galaxies to study in detail the evolution of gas and dust during this early growth phase of galaxy evolution. ALPINE builds the basis sample and anchor for the comparison to surveys at lower and higher redshifts as well as to state-of-the-art simulations. Some of these galaxies may harbor accreting black holes and some may be on the verge of being quenched. With follow-up programs with existing (HST, JWST) and future (Euclid, Roman, SPHEREx) facilities, we will be able to study the beginning and fate of these galaxies.

Spherical symmetry breaking in the transition from Red Giant to Planetary Nebula, and the mechanism that governs it, have been a topic of intense interest for decades. Recent observations with high sensitivity and angular resolution have shown that spherical symmetry breaking was already present, in many cases, in the early AGB phase. At large distances from the star the circumstellar envelopes of AGB stars have been shown very complex with many fragments in the form of bipolar outflows, blobs, arcs and spirals. At smaller distance, the nascent winds share some features which need to pay attention including the presence of line broadening in the inner layer, the strong absorption of SiO emission over and beyond the stellar disc and the rotation within 30 au or so from the star. In this presentation, I will review the properties of their circumstellar envelopes (CSE) and their nascent winds with the aim of revealing significant similarities or differences in the hope of improving our understanding of the mechanisms at stake.

The general picture of planet formation is well agreed: planets are formed within a few million years after the collapse phase in a protoplanetary disk surrounding the protostar. However, the detailed formation conditions and mechanisms are still debated, requiring more sophisticated studies both in theoretical, modeling, and observations. A substantial portion of observed exoplanets is found in binary or higher hierarchical systems. Therefore, studying the physical properties and chemical contents of the protoplanetary disk in binary/multiple systems is essential to understand the formation and variety of planetary systems. I will present a study of GG Tauri A using sub-millimeter observations carried out with ALMA and NOEMA interferometers. GG Tauri A is the prototype of a young triple T Tauri star that is surrounded by a massive and extended Keplerian outer disk. The central cavity is not devoid of gas and dust and at least GG Tauri Aa exhibits its own disk of gas and dust emitting at millimeter wavelengths. Its observed properties make this source an ideal laboratory for investigating planet formation in young multiple solar-type stars. A general picture of gas properties and dynamics from the cavity to outer disk as well as its chemical content and the hint of planet(s) in formation in the circumbinary disk of GG Tau A will be presented.

박성현 서울대학교 명예교수(자연과학대학 통계학과)님께서  다음의 네가지 주제로 1시간 정도 발표해주실 예정입니다. 1. 에너지 사용 현황과 전망 2. 기후변화 3. 재생에너지와 원자력 4. 탄소중립 2050과 과학기술정책

In order to answer the fundamental open question of ``Where do nuclei and elements come from'', studies of nuclear properties with powerful rare isotope beam (RIB) facilities are critical. Moreover, with the recent astonishing observation of the first neutron star merger by astronomers, understanding nuclear spectroscopic properties of short-lived nuclei has become very important to demonstrate outcomes of the event such as gamma-ray, optical and X-ray emissions. However, because most of the key nuclei constraining the nucleosynthesis models including the rapid proton capture process (rp-process) and the rapid neutron capture process (r-process) are far from stability, our understanding of astronomical observables is still very limited due to large uncertainties in calculated properties of the nuclei and a lack of measurements with radioactive ion beams for the spectroscopic information. While there are a few RIB facilities in the world, which provide short-lived radioactive beams to perform studies of nuclear properties of exotic nuclei, new generation RIB accelerator facilities around the world including FRIB in the U.S., RIBF in Japan and RAON in Korea will be available soon. Recent experimental studies of key nuclei performed at the existing facilities will be presented as well as new active research activities at the Center for Exotic Nuclear Studies (CENS), Institute for Basic Science (IBS). Future plans on how to take advantage of the new facilities including RAON will also be addressed.

Digital humanities, as the intersection of computing and the disciplines of the humanities, have offered new opportunities for teaching and research innovation that complement the traditional approach in the humanities. While surveying the past, present, and future studies in the humanities, this lecture explores how the digital transformation will influence science classics.

This year marks the 30 years to launch the first Korean satellite KitSat-1. South Korea is now on the verge of entering the space economy era based on technological capability in the space sector and increased private capacity. The talk will illustrate the process of Korea's space development system from a historical point of view, first, and will touch on the policy issue related the limitations of the current national space innovation system, including governance, government R&D, space industrialization, space security/defense, international cooperation for exploration and diplomacy, and so on.

The protostellar phase, an early phase of star formation, has recently gained the spotlight as a phase for planet formation. On the other hand, the place of planet formation, “disk”, is difficult to identify in the protostellar phase because disks are embedded in envelopes in this phase. Identifying a disk also tells us the most important parameter of the protostar, central stellar mass M*. Previous works reported observational identification of disks in protostellar systems. The method is, however, different from work to work. To verify the consistency among different methods, I applied representative methods to synthetic observations using a magnetohydrodynamic simulation of protostellar evolution. This test demonstrates that a method using position-velocity diagrams can estimate the disk size and the central stellar mass accurately, particularly when M* >~ 0.2 Msun. Our group has been using this method with SMA and ALMA observations almost for a decade and are continuing to develop it. Even after a disk is identified in a protostar, the system provides questions related to the disk and planet formation: e.g., how the disk obtains mass or how dust grains grow in the disk. I introduce a case study of the protostar TMC-1A to investigate these questions, based on dust continuum, spectral line, and dust polarization observations using the SMA and ALMA. In addition to these studies I accomplished in KASI, I would also like to review my activities in KASI during the ~3-yr term.

Coronal mass ejections (CMEs) are among the most energetic and powerful solar phenomena. The CMEs transfer solar energetic particles to the Earth and cause geomagnetic storms, which can produce severe space weather conditions. Previous studies have found that the CME plasmas are strongly heated in the low solar corona. Also, ion charge compositions from in situ measurements have shown that ionization state models require strong and rapid heating around 2 R⊙. In addition, solar coronal plasma is often interpreted assuming equilibrium ionization and Maxwellian electron velocity distributions. But, if the thermodynamical timescale in a rapidly evolving system is shorter than the ionization and recombination timescale, then the plasma can be far from the equilibrium ionization state because of rapid heating or cooling. Non-Maxwellian electron distributions can be caused by particle acceleration, turbulence, or shocks. High-energy observations show that their particle velocity distributions reveal suprathermal tails, which Kappa (κ) distribution functions can represent. In this talk, I introduce previous studies of the heating of CME plasmas using the observations by UV coronagraph spectrometer and EUV and X-ray imaging observations. And I present how we study the heating of the nonequilibrium state coronal plasmas by comparing in situ observations such as interplanetary coronal mass ejection and solar wind. 

SI Analytics는 쎄트렉아이의 자회사이자 인공지능 기반 위성 항공 영상 분석 전문기업으로 지구 관측을 통해 현명한 결정을 하기 위한 가치를 제공한다. SI Analytics 인공지능 연구소는 객체 탐지, 변화 탐지, 초해상화 등의 다양한 인공지능 모델을 개발하고, 위성 데이터로부터 국방, 기상, 기후 변화 등 지구 관측과 관련된 다양한 주제에 대해 분석하여 정보를 제공하고 있다. 최근 연구소는 사회적으로 이슈인 ESG (Environment Social Governance) 의 주요 키워드인 탄소 중립의 중요성과 탄소 배출량 측정 방법의 한계를 인지하고, 정부의 2050년 탄소 중립을 실현 하기 위해 배출량 산정 근거가 될 수 있는 위성 관측을 활용한 인공지능 기반 탄소 배출량 측정 기술 연구를 시작하였다. 현재 탄소 배출량은 위성 또는 현장 관측을 통해 다양한 방법으로 측정되고 있지만, 관측 방법의 다양성과 관측으로부터 탄소 농도를 산출하는 모델의 다양성으로 인해 일관성 있는 분석에 어려움이 있다. 따라서 탄소 분포와 농도를 같은 기준으로 감시, 관리하기 위해서는 표준화된 측정 데이터 제공이 필수적이다. 위성은 전 지구를 같은 센서로 관측하고 있으며, 점차 고해상도 관측이 가능해 지고 있기 때문에, 탄소 측정에 매우 중요한 수단이 되고 있다. 따라서 본 연구자는 이러한 사회적 필요성에 발맞추어 탄소 관측  OCO-2 위성 데이터를 활용하여 Level 1b 자료를 Level 2 로 변환하는 물리기반 역변환 모델을 인공지능 모델이 대치할 수 있는지에 대한 가능성을 확인하고, 그 결과에 대해 소개하고자 한다. 

가장 오랜 역사를 갖고 있는 학문 중 하나인 천문학은 관측과 함께 시작했다. 이러한 관측은 데이터를 만들고 이러한 데이터를 분석하는 다양한 기법들이 함께 발전했다. 빅데이터라는 용어가 나오기 전부터 천문학자들은 대용량의 데이터를 분석하고 이를 이용해 물리 법칙을 증명해왔다. 이러한 경험을 바탕으로 최근 천문학 전공자들이 데이터과학 분야로 뛰어들고 있으며 다양한 도메인에서 데이터과학자로서 역할을 해내고 있다. 본 발표에서는 천문학 전공자로서 겪은 데이터과학과 인공지능 기술에 대해 공유하고, 이러한 최신 기술들이 어떻게 의료 분야에서 적용되고 상용화까지 이르고 있는지 소개하고자 한다. 

In this talk, we would like to discuss how large-scale filaments affect the evolution of galaxies. By analyzing the HORIZON-AGN simulation data at a fixed redshift of z~2, we found that the dependency of galaxy properties on large-scale environment is mostly inherited from the (large-scale) environmental dependency of their host halo mass. When adopting a residual analysis that removes the host halo mass effect, we detected a direct and non-negligible influence of cosmic filaments. Proximity to filaments enhances the build-up of stellar mass. However, our multi-scale analysis also reveals that, at the edge of filaments, star formation is suppressed. We suggest that gas transfer from the outside to the inside of the haloes (where galaxies reside) becomes less efficient closer to filaments, due to high angular momentum supply at the vorticity-rich edge of filaments. To understand the underlying causality of such impacts of filaments on galaxy properties more directly, it is needed to track individual galaxies in time. Along that direction, we first tracked galaxy-hosting halos using a dark matter-only simulation. We examined the settling process of halos into the filament potential well in a phase space and their mass evolution along with it. Halos’ orbital trajectories and mass evolution are determined quite much by the initial condition of halos (i.e., initial position and formation time), which are also affected by the density of filaments. We found the mass segregation around filaments as with observations, which can be explained with massive halos being those that arrived filaments earlier. 

Since physical processes in the magnetopause can be observed in the high-latitude ionosphere via field lines and current systems, ground magnetic field responses to solar wind and IMF changes can provide valuable information on dayside transient phenomena involved in solar wind-magnetosphere-ionosphere coupling process. The basic processes at the magnetopause boundary are magnetic reconnection, and viscous-like interaction, such as Kelvin-Helmholtz instability (KHI) and pressure-pulse drive. The magnetic reconnection occurs preferentially at the region where magnetosheath largest when the IMF is southward. On the other hand, the KHI is generally known to be driven by the velocity shear with a rapid magnetosheath plasma at the boundary for northward IMF condition. The magnetosphere boundary can also fluctuate in response to solar wind dynamic pressure pulse. However, it still need to be understood what kind of factors of magnetopause boundary are more important depending on the solar wind and IMF conditions. We have studied magnetospheric dynamics and ionospheric phenomena by using a high-resolution 3-D global MHD simulation of the solar wind and planetary magnetosphere interaction as a function of IMF condition. The results of these studies will be presented.

The isotope ratio of molecules is a powerful tool for investigating the origin of solar system materials and for revealing the possible chemical link between the solar system and the interstellar medium. More and precise isotope ratios have been quantified through spacecraft missions to various solar system bodies and the high sensitivity ALMA observations of molecular isotopologues in star and planet forming regions.  Furthermore, the development of numerical modeling considering detailed gas-phase chemical networks with grain surface reactions, has improved our understanding of isotope chemistry. In this talk, I will present observational and theoretical progress of isotope ratios, especially the nitrogen and carbon isotope ratios, in the protoplanetary disks. 

The elemental abundance in the solar corona is different from the photosphere. The fractionation between photospheric and coronal abundances is related to the “First Ionization Potential (FIP) effect.” In the corona, the low FIP (FIP < 10 eV) elements are enhanced by factors of 3–4 relative to the photospheric abundances. In contrast, the high FIP elemental abundance ratio to photospheric is approximately equal. Still, it is not revealed how the solar abundance is fractionated. Recently, the most probable model is “Abundance fractionation by the Pondermotive force”. The pondermotive force induced by the Alfvén wave preferentially affects the ionized elements (low FIP element), not the neutral in the chromospheric plasma, which is partially ionized. Then, the force drags up (or down) the low FIP elements depending on the Alfvén wave existence and their energy density in the chromosphere. For investigating the relations between the abundance fractionation and wave energy density in the chromosphere, we analyze the H alpha and Ca II data from GST/FISS for the Alfvén wave detection and Si X (low FIP element) and S X (high FIP element) spectra from Hinode/EIS for determining the relative abundance in an active region. We present the result of detecting Alfvén waves in the chromosphere compared to the spatial distribution of the abundance fractionation.

OB associations are large stellar systems composed of groups of young stars spread over several tens of parsecs. They are the prime sites of star formation in galaxies. More than one stellar cluster and distributed stellar populations are found in such stellar systems. This is a general structural feature. It has been believed that such structural features may contain a clue to the formation process of OB associations because OB associations are young. Before the Gaia undertook its own mission, it was very difficult to obtain homogeneous observational data for various associations distributed over wide sky areas. Furthermore, the selection of members was even more limited. The Gaia mission has now opened a new window to study OB associations in detail as it measures the precise parallaxes and proper-motions of stars in the Galaxy. In this talk, I will present the observational results of several galactic OB associations and discuss their formation process. 

The distribution of galaxies in the low redshift Universe provides information on the initial conditions, energy content and evolution of the Universe from its almost Gaussian primordial state to the highly non-linear cosmic web that we observe today. In this talk I will introduce a class of statistics that are capable of extracting both Gaussian and non-Gaussian information from the matter distribution. The so-called Minkowski Functionals and their rank-2 tensorial generalisation are a class of topological descriptors of a field which can be used to measure cosmological parameters, test the degree of non-Gaussianity as a function of scale and also provide a mechanism to test statistical isotropy. I will describe these statistics, explain how we extract them from galaxy catalogs and elucidate what they can tell us about the properties of the Universe. 

Planet formation is one of the hottest topics in astronomy especially owing to the recent developments of ALMA observations of protoplanetary disks. Dust grains, which are the seeds of planets, coagulate to form larger and larger bodies, and finally form into thousand-kilometer-sized planets. One of the key observational constraints are on the dust mass and size, which directly constrain planet formation theories. In this talk, I will first review the recent observations of protoplanetary disks especially focusing on the observational constraints on dust grains. Then, I will discuss polarimetric observations of protoplanetary disks with ALMA. One of the dominant mechanisms is now believed to be the self-scattering, which allows us to constrain the dust sizes. However, the new measurements make the tension between the classical understandings of millimeter-sized dust grains and the sub-mm size dust grains with the new polarimetric constraints. I will discuss possible solutions and their impact on planet formation.