Prior to the year 2005, the number of known “classical” Milky Way (MW) dwarf satellite galaxies (?8 mag > Mv > ?18 mag) remained twelve. However from 2005 to the present, thanks to the high quality photometric data from extremely well designed systematic surveys such as Sloan Digital Sky Survey (SDSS; York et al. 2000) or Dark Energy Survey (DES; Abbot et al. 2005), the number of newly discovered faint dwarf satellites has dramatically increased: Now we have almost forty dwarf satellite galaxies in the halo of the Milky Way (e.g., 15 ultra-faint dwarfs from SDSS; 17 dwarf galaxy candidates from the first two-year data set of DES), and there might be more than tens of faint dwarf satellites still waiting to be discovered in the near future (Koposov et al. 2007; Tollerud et al. 2008). In this talk, I will give a quick guided tour on these near-field dwarf galaxy populations. For in-depth review, we will take a look at several specific case studies on the properties of dwarf satellite galaxies in the Local Group and nearby Sculptor filament. Finally I will close my talk by introducing the usage of “RR Lyrae variable stars” as a versatile probe to “old stellar halos” of nearby galaxies.

The World Space Observatory Ultraviolet (WSO-UV) is the space mission that will grant access to the UV range in the post Hubble epoch. WSO-UV is equipped with instrumentation for imaging and spectroscopy and it is fully devoted to UV astronomy. In this talk, we outline the WSO-UV mission model and present the current status of the project. Also, the NEO observing mission SODA (System of Observation of Day-time Asteroids) is also presented.

The ASIAA is leading an effort to deploy the 12m ALMA-NA prototype telescope to the Summit of Greenland. We have been retrofitting this telescope for operations at polar conditions, and we will ship the telescope to Thule in Greenland in 2016. The scientific target is to image the shadow of the supermassive black hole in the nucleus of the M87 galaxy. Although at a distance of 18Mpc, the M87 SMBH is almost as large in apparent size as the SgrA* SMBH in the Milky Way. The shadow is expected to be on the order of 40 micro arsec. By using the GLT as the northern station of a VLBI experiment which will include ALMA, the SMA, and the JCMT, we aim to achieve 20 micro arsec resolution at 350GHz. The GLT will be the first astronomical observatory in the Arctic region. In this talk, we will report on the current status of this project.

Gamma-Ray Bursts (GRBs) are the most energetic explosions in the universe. We have already known the most distant GRBs at the redshift z=8.26 (spectroscopic) and z=9.4 (photometric), so we can use GRBs as the cosmological probing tool. However we could obtain little knowledge of physical conditions in the early universe from these high-z GRBs while their redshifts were measured. We hope to perform the high dispersion spectroscopy with the large area telescopes during the afterglows are still bright. Then we can challenge to reveal the reionization epoch and the origins, early metal enrichment, star formation history as well as to detect GRBs from first stars (population-III stars). Japanese GRB community has organized a working group of a future small satellite mission, named "HiZ-GUNDAM" (High-z Gamma-Ray Bursts for Unraveling the Dark Ages Mission), to pioneer the observation of early universe with high-z GRBs. This mission consists of two instruments, the X-ray imaging system with coded aperture mask and the optical/near infrared telescope with 30cm diameter. Once GRBs are detected and localized, HiZ-GUNDAM rapidly perform the follow-up observation like the Swift satellite, and determine the rough redshift with the photometric observation with the optical/NIR telescope. The onboard measurement of redshift and the redshift alert system will play an important role in leading the follow-up observation for the early afterglows by large area telescope. The X-ray imaging system continuously monitors a large field of view of ~1 steradian in the energy range of 1-20 keV with the effective area of 500-1,000 cm2. We are developing 1-dimensional silicon strip sensor with the size of 19.2mm x 16mm (~3 cm2), and which has 64ch strip-type electrode with the width of 0.3mm. We are also developing the 64ch specific ASICs which is modified version of ones developed by Prof. Takahashi and Prof. Ikeda group in ISAS/JAXA. According to the current simulations by T-SPICE electric circuit simulator, they have enough gain to readout the small charges from 1 keV X-ray photon, and we can integrate appropriate trigger system. Using the coded aperture mask with the same pitch of 0.3mm at the distance of 30cm from the detector plane, we can determine the position of GRBs with ~10 arcmin accuracy in geometrically and ~5 arcmin for bright GRBs. Since the high-z GRBs have low brightness with long time duration because of the cosmological time dilation, we will enhance so-called imaging trigger system. The optical/NIR telescope has the primary mirror with 30cm in diameter, and we consider the offset Gregorian optics to avoid the stray light from the sun and the earth. We will divide the optical ray of 0.5--1.7 um into 4 bands with dichroic mirror, and perform the photometric observations and select the candidates of high-z GRBs. A reflection baffle (aperture shade) in front of the telescope gives us the wide visibility larger than the field of view of X-ray imaging system. Therefore we effectively perform the follow-up observations for GRBs detected by the X-ray detector. In this talk, we introduce the concept of HiZ-GUNDAM mission and the developing/planning instrumentations.

Despite the fact that the APOGEE project is focused on the structure of the galaxy, it also offers a lot to explore for stellar astrophysicists. In this colloquium, I will talk about two projects which are using the dwarf M (dM) stars in APOGEE. The first project is searching for HW Vir type (subdwarf B (sdB) + dM / brown-dwarf) systems, which are believed to compose a high percentage of subdwarfs despite not proven yet. The aim is to look at the IR spectra of dM stars in order to find a trace of an sdB companion. The results would reveal the binarity nature of sdB stars and common-envelope evolution, and contribute to the theoretical and evolutionary studies of sdBs through dM stars. The second project is to to define a chromospheric activity indicator in IR region by using active and inactive dwarf M stars' spectra and determine candidates for a 'Chromospherically Active Cool Stars Survey'.

The planet crossing asteroids in the inner solar system have strongly chaotic orbits and the distributions of their angular elements are often regarded as uniform random. We quantified the level of intrinsic non-uniformities of the angular elements for the dynamical subgroups of Near Earth Objects (NEOs) and Mars Crossing Objects (MCOs). Using the methods of angular statistics, we found several statistically significant departures from uniform random angular distributions. These non-uniform distributions of the angular elements may affect the asteroidal impact fluxes on the planets. We developed a new approach that accounts for the non-uniform angular elements of planet crossing asteroids to investigate the impact flux and its seasonal variation on the Earth, the Moon, and Mars. The impact flux of NEOs on the Earth-Moon system is found to be not affected significantly by the non-uniform distribution of angular elements of NEOs. The impact flux on Mars, however, is found to be reduced by a factor of about 2 compared to the flux that would obtain from the assumption of uniform random distributions of the angular elements of MCOs. Moreover, the impact flux on Mars has a strong seasonal variation, with a peak when the planet is near aphelion. We found that the amplitude of this seasonal variation is a factor of 4-5 times smaller compared to what would be obtained with a uniform random distribution of the angular elements of MCOs. We calculate that the aphelion impact flux on Mars is about three times larger than its perihelion impact flux.

The European Southern Observatory (ESO) is an intergovernmental astronomy organisation that provides state-of-the-art research facilities in Chile to astronomers in Europe and all over the world. Engineers, administrative staff, astronomers, scientists and many more, based in Chile and Germany, work together to keep ESO one of the world's most productive astronomical observatories. ESO astronomers are also very active in their own research fields, covering topics from exoplanets to high-redshift cosmology. I will give a brief introduction about the current activities of ESO and will highlight how ESO astronomers manage to combine their functional work with conducting forefront science. In the second part of my presentation, I will focus on my own scientific work. More than 16 years ago, so-called 'Ultra-Compact Dwarf galaxies' (UCDs) have been discovered in spectroscopic surveys of the Fornax galaxy cluster by our team. UCDs have a special place in the fundamental plane of pressure supported stellar systems. They are located at the high mass end of the globular cluster (GC) distribution, reaching ~10^8 M_sun and obey a mass-size relation unlike 'classical' GCs, but connecting to compact ellipticals. Nowadays, dozens, if not hundreds, of UCDs and their fellow `dwarf galaxy transition objects' (DGTOs), `giant globular clusters' (GGCs) and `extended clusters' (ECs) have been identified in various environments, filling the space in the fundamental plane between star clusters and dwarf galaxies. I will review the knowledge we obtained over the last 16 years of these sometimes still puzzling objects. I will present the occurence, spatial distribution, dynamics and mass spectrum of UCDs in different environments. For some of the bright UCDs, internal properties (metallicity, ages, [alpha/Fe] abundances, internal kinematics, clues to their IMF, etc.) are available, which I will highlight. Finally, I will summarize our current ideas about their formation and will conclude that the majority of UCDs belong to the 'star cluster family'.

Circumstellar disks of young stellar objects (YSOs) at a later stage are often called protoplanetary disks, as they are the natal place of protoplanets. In this talk, we present continuum observations at λ = 1.3 and 2.7 mm using the Combined Array for Research in Millimeter-wave Astronomy toward six protoplanetary disks in the Taurus molecular cloud: CI Tau, DL Tau, DO Tau, FT Tau, Haro 6-13, and HL Tau. We constrain physical properties of the disks with Bayesian inference using two disk models: the flared power-law disk model and flared accretion disk model. Comparing the physical properties, we find that the more extended disks are less flared and that the dust opacity spectral index (β) is smaller in the less massive disks. In addition, disks with a steeper mid-plane density gradient have a smaller β, which suggests that grains grow and radially move. We also discuss the possibilities of substructures on three extended protoplanetary disks. Furthermore, the HL Tau disk images taken by the Atacama Large Millimeter/submillimeter Array (ALMA) are shown and discussed. If time is allowed, disk formation at earlier stages of YSOs would be addressed as well.

We have explored GALEX UV properties of optical red sequence galaxies in 4 rich Abell clusters at z ? 0.1. Inparticular we tried to find a hint of merger-induced recent star formation (RSF) in the red sequence galaxies. RSF fractions are calculated with various criteria for post-merger galaxies and normal red sequence galaxies based on their NUV - r’ colors. In this study it turned out that only 30% of the RSF red sequence galaxies involve tidally-disturbed features in cluster environment. It is possible that we are missing minor merger features with the deep optical images from the less massive regime (-21 < Mr' < -20) of our volume-limited sample. However, considering the timescale difference for the fading out of morphological merger features (~ 4 Gyr) and young stellar populations (~ 1 Gyr), the fraction of RSF red sequence galaxies without disturbed features is still significantly large. We also confirmed that those featureless RSF galaxies are mostly bulge-dominated. This result may imply that gas accretion in early-type galaxies plays a significant role in residual star formation of the early-type galaxies.

A number of different scenarios have been proposed to explain the formation of massive stars. These include formation through the merger of less massive stars (coalescence model) or through the accretion of unbound gas from the molecular cloud (competitive accretion model). In the third scenario, the core accretion model, massive stars form through gravitational collapse, which involves disc-assisted accretion to overcome radiation pressure. This scenario is similar to the favored picture of low-mass star formation. Despite the likely importance of magnetic fields in the formation of low-mass stars, there are still only a few observations around massive stars, and theoretical simulations match the observations as long as the magnetic field is taken into consideration. Therefore, providing new measurements of magnetic fields orientation and strength at milliarcsecond resolution is fundamental to understand the formation process of high-mass stars. The best probes of magnetic fields in the high density regions close to massive protostars currently available are masers. In particular 6.7-GHz methanol and 22-GHz water masers. In the last six years we have studied the magnetic field around several massive young stellar objects by observing the polarized emission of water and, mainly, methanol masers. In my colloquium I will go through the results that we have achieved so far by emphasizing the most interesting cases.

Ghana has been enjoying space products for its socio-economic development for decades. Therefore, the idea of Ghana Space Science and Technology Center was conceived in 20008 but it was not until 2011 that the Centre was officially launched. The Centre has subsequently been upgraded into an Institute with three (3) research Centers, namely Radio Astronomy and Astrophysics, Remote Sensing and Climate Change, and Satellite Communication and Engineering. The Institute‘s mandate is to exploit the capabilities of Space Science and Technology for socio-economic development and to coordinate all Space related activities in Ghana. The Institute is engaged in joint projects and collaborations with partners globally. This presentation is to give an overview of activities at the Institute and also to showcase the opportunities for joint projects, capacity building and partnerships.

The Kepler space mission has discovered many planets around other stars, some of which are in the so-called habitable zone. In order for these planets to harbour terrestrial-type life, it is imperative that they experience a stable climate on long time scales. Earth experiences regular ice ages caused by perburbations from the other planets that cause the so-called Milankovic cycles. Such climate changes induced by the dynamics of the planetary system must be kept to a minimum. Here we report a case study of long-term climate cycles on the super-Earth HD 40307 g and extend this methodology to other systems.

Evolution of massive stars is determined by several important physical processes that we still do not fully understand theoretically. They include stellar wind mass loss, binary interactions, and stellar rotation. Interestingly, these three primary factors for the evolution of massive stars are closely related to production of hydrogen-deficient massive stars. The best known example is Wolf-Rayet stars: it is believed that the hydrogen-rich envelopes of their progenitors have been stripped off via stellar winds. Binary interactions and rotationally-induced chemical mixing can also make important contribution to the production of hydrogen-deficient stars. Wolf-Rayed stars and other forms of hydrogen-deficient stars (e.g., helium stars in massive binary systems) may produce a number of ionizing photons, and eventually explode as core-collapse supernovae of Type IIb, Ib and Ic or as long gamma-ray bursts depending on their final structure at the pre-collapse stage. Observing these stars and their explosions would therefore provide excellent constraints for stellar evolution theory. In this talk, I will review evolutionary scenarios of massive stars towards hydrogen-deficient stars, and their confrontation with recent observations.

Since 1964, NASA has sent flybys, orbiters, landers, and rovers to Mars, and is ready for a sample return mission in 2020’s and human exploration in 2030’s. In my talk, we will look into the cultural and historical background of Mars exploration, and overview past, present, and future NASA missions while updating Curiosity’s findings as of May 2015. We will examine NASA Mars missions’ impact on science, and technology, STEM education, and economy. Furthermore, we will go over NASA’s readiness for human exploration and the significance of Mars missions to our future generations. Lastly, I will update the international collaboration in NASA Mars missions. NASA는 지난 1964년부터 화성으로 비행선과 궤도선, 착륙선, 로버 등을 보냈으며 2020년대에는 시료 귀환임무를, 2030년대에는 유인탐사 임무를 준비하고 있습니다. 이 강의에서는 화성탐사의 문화적, 역사적 배경과 과거, 현재, 미래의 화성 탐사에 대해 소개하고 최근 발표된 큐리오시티의 탐사 결과를 알려 드리겠습니다. 또한 NASA의 화성 탐사 임무가 과학과 기술, 교육, 그리고 경제에 미치는 영향에 대해 말씀드리겠습니다. 아울러, NASA의 유인탐사 계획이 지금까지 얼마나 준비되었는지, 화성탐사가 미래 후손들에게 어떤 의미를 주는지 이야기 해보고 싶습니다. 마지막으로 화성탐사 임무에 관련된 NASA의 국제협력에 대해 말씀드리겠습니다.

Walter Baade, late in his career, was asked if he would choose a career in astrophysics if he had to do it all over again. He replied yes, but only if he could be assured that the ratio of total to selective dust extinction was universally 3. Many of us might add that we would want to be assured that the stellar initial mass function is also universal. Unfortunately, evidence is mounting that it is not. Of course, one person's misfortune is often another's gain - so perhaps variations in the IMF will help generate insights into a better understanding of star and galaxy formation. I will discuss an examination of this topic using Local Group dense star clusters.

무인기 군집 비행 기술 소개 - 임무 계획 기법을 중심으로

The deep gravitational potential wells of clusters of galaxies should capture fair samples of the total baryon fraction of the Universe, unless other physical processes drive baryons out of clusters. Thus precision measurements of the baryon fraction, particularly as a function of cluster mass, can reveal the history of baryon flux into and out of clusters. How those baryons are then apportioned between stars and intracluster gas---the star formation efficiency---informs models of cluster assembly and massive galaxy evolution, as well as efforts to use the cluster gas fraction to constrain the mass density and dark energy equation of state parameters. Even the partitioning of the stellar baryons alone, in and out of galaxies, tests models of cluster galaxy evolution, as intracluster stars are the final, unambiguous signature of stars stripped from cluster galaxies during tidal encounters. We have discovered that intracluster stars are a significant part of the stellar baryons in clusters and poorer groups of galaxies. I will present new work, including HST observations, characterizing the properties of this previously unexplored component, as well as the consequences for the cluster baryon budget and its relationship to the Universal value.

The objective-prism surveys such as HK and Hamburg ESO (HES) discovered numerous Very Metal-Poor (VMP; [Fe/H] < -2.0) stars in the Milky Way. Recently, the number of VMP stars has been dramatically increased to many tens of thousands, thanks to Sloan Digital Sky Survey (SDSS) and Sloan Extension for Galactic Understand and Exploration (SEGUE). Detailed chemical-abundance analyses, based on high-resolution spectroscopic follow-up, have revealed that, while most VMP stars exhibit similar abundance patterns, there are numerous examples of objects with peculiar chemical patterns. Among the chemically peculiar stars with [Fe/H] < -2.0, objects with enhanced carbon abundance are the most common variety. These are called Carbon-Enhanced Metal-Poor (CEMP) stars. One of the most interesting aspects of the CEMP stars is that the fraction of the CEMP stars increases as the metallicity decreases. In this talk, I will review the current understanding of the CEMP stars and discuss their implication to the first-generation stars and the origin of the Milky Way galaxy.

The ESA’s geomagnetic field mission, Swarm is composed of three satellites equipped identically with the Absolute Scalar Magnetometer (ASM), Vector Field Magnetometer (VFM), Langmuir Probe (LP), Thermal Ion Imager (TII), and Accelerometer. The three satellites were launched into the same altitudes (~500 km) with an orbit inclination angle of 87.3o. During the first two months the satellites were flying in a pearls-on-a-string configuration. Between February and April 2014 the spacecraft conducted orbit maneuver. Since 17 April 2014 the lower satellites, Swarm-Alpha and Swarm-Charlie have been flying side-by-side at altitudes around 470 km. The upper satellite, Swarm-Bravo flies higher by about 50 km, with the orbital plane being separated gradually from that of the lower satellite pair. Observation of ionospheric irregularities by the multiple Swarm satellites can help elucidate 3-dimensional morphology of the ionospheric irregularities. Selected examples of plasma density irregularities observed by Swarm are described in detail and discussed during this presentation.

Debris disks are the leftovers of planetary formation, revealing collisional debris from exo-Kuiper belt objects. Traditionally debris disks are found by deep searches of known nearby stars within 100 pc, which places obvious limits on the sample sizes that can be studied. Here I will outline a search technique utilising deep multiwavelength extragalactic surveys that opens up a radically new search space for debris disks and can reveal examples of disks that are too rare to exist in the local volume.

- Planetarium의 정의 - Planetarium의 탄생과 발전 - 우리나라 최초의 Planetairum과 역사 - 세계/우리나라 Planetairum 분포와 통계 - Planetarium의 역할과 미래

The Square Kilometre Array (SKA) project, which is the world-biggest international cm/m radio interferometer project, is now in the pre-construction stage 1 during which the SKA organization (SKAO) proposes options of elements and systems of the first 10 % construction of SKA called the SKA phase 1 (SKA1). SKAO has been re-baselining the SKA1 according to realistic costs and scientific updates since a release of the SKA1 system baseline design in March 2013. The re-baseline will be approved by the SKA board in early March. As for a science side, the science team in SKAO conducted an update of an international SKA science book. More than 120 chapters were proposed and accepted for publication last year. Finally, in Japan, NAOJ has started financial supports for Japanese SKA activities since last year. I am visiting in SKAO on secondment to play a role of a liaison, supported by NAOJ and SKAO. Japanese SKA science working groups have edited a Japanese SKA science book, in which they reviewed Japanese sciences with SKA. I will talk about these progress related to the SKA project.

In this talk, the multi-core fiber Bragg gratings (MCFBGs) is introduced and it is shown how they can be used in the astronomical purpose. Furthermore, the current status of the MCFBG development will be presented. Fiber Bragg gratings (FBGs) are the most compact and reliable method of suppressing atmospheric emission lines in the infrared for ground-based telescopes. Standard single core FBG based filters (GNOSIS) were demonstrated in AAT to eliminate 63 OH lines in 2011 and in . Inscribing FBGs on multi-core fibers offers advantages. Compared to arrays of individual single mode fibers (SMFs), the multi-core fiber Bragg grating (MCFBG) is greatly reduced in size, resistant to damage, simple to fabricate, and easy to taper into a photonics lantern. AAT and the University of Sydney are developing the next generation of GNOSIS (PRAXIS). In addition, I would like to briefly introduce various instruments for the astronomical purpose in Astrophotonics group of AAO and the University of Sydney including an optical angular momentum (AOM) measurement as well as a microspectrograph (NanoSpec), which is the world’s first photonics-based spectrograph and have been developed to be shipped in a micro-satellite (i-Inspire). The i-Inspire has been tested in a weather balloon in 27 km altitude in 2012 and will be launched. The arrayed-waveguide-grating (AWG) based filter development will also concisely be presented.

This talk is a review of the current status of the luminosity function for broad-lined unobscured AGN, along with implications for triggering and black hole growth, and a look at the unresolved issues. It is inspired by the 50th anniversary in 2013 of Schmidt’s discovery of the nature of the quasar redshift to reflect on the state of knowledge and context of early determinations of the quasar luminosity function vs. those today. The rapid evolution of the high-z luminosity function holds some promise for differentiating the physical processes responsible for triggering ? mergers, “cold flow”, or instabilities within the hosts. More data are still needed, particularly to characterize the faint end of AGN activity.

Recent developments in CMB and large-scale galaxy surveys have led to the standard cosmological model, but the physical understanding of its ingredients remains elusive so far. In response to the gravity of these issues, numerous large-scale galaxy surveys are ongoing or planned to be operational in a near future. However, precision measurements in future galaxy surveys bring in new challenges, demanding substantial advances in theoretical modeling and observational methods. I will discuss the recent theoretical development in modeling galaxy clustering in a relativistic context and the observational issues associated with this recent development. The relativistic effect in galaxy clustering or the deviation from the standard Newtonian description becomes substantial on large scales, in which dark energy models or alternative theories of modified gravity deviate from general relativity, and in which the fingerprint of the inflationary epoch remains in its pristine form. I will discuss how the subtle relativistic effect in galaxy clustering can be used to test general relativity on large scales and probe signatures of the early Universe.

The existence of the dark matter has been strongly supported from the cosmological observations such as the stellar rotation curves of spiral galaxies and the CMB measurements. The origin and nature of the dark matter however remain largely unknown, which has been among the most active research avenues in both particle physics and cosmology. This talk will give a theoretical overview on the current status of the dark matter studies, along with the examples for the attempts to search for them from the high energy physics and cosmology experiments.

Crowded regions of the sky present a significant challenge for stellar photometry. I will discuss how we use difference-imaging to extract the signals from variable stars from the background of constant-brightness objects, and show some examples from the KMTNet microlensing survey of the Galactic Bulge. I will briefly discuss the use of Graphical Processing Units (GPUs) for parallel computations in astrophysics, and describe pyDIA, a new GPU-based code for wide-field difference-imaging photometry.

Stars are opaque, so how can we work out their interior structure and the physical processes that are occurring inside them? Asteroseismology is the science of deducing stellar interiors from observations of a star’s surface oscillations. By monitoring a star’s tiny surface vibrations with a precision spectrograph, we can calculate that star's unique frequencies and modes of vibration, which are wholly governed by its interior structure. In this way, we can obtain tight constraints on the conditions within the star, which allows us to probe the relationship between the interior structure and the evolution of stars. In this talk, I will describe our observing programme at the University of Canterbury’s Mt John Observatory, where we obtain extensive high-resolution echelle spectra of non-radially pulsating stars. We analyze these to obtain the pulsational frequencies and identify these with the multiple pulsational modes excited in the star. I will present a summary of our observational program and some recent results from our spectroscopic frequency and mode-identification analysis.

Intensity interferometry, based on the Hanbury Brown--Twiss effect, is a simple and inexpensive method for optical interferometry at microarcsecond angular resolutions; its use in astronomy was abandoned in the 1970s because of low sensitivity. Motivated by recent technical developments, we argue that the sensitivity of large modern intensity interferometers can be improved by factors up to approximately 25,000, corresponding to 11 photometric magnitudes, compared to the pioneering Narrabri Stellar Interferometer. Our approach permits the construction of large (with baselines ranging from few kilometers to intercontinental distances) optical interferometers at the cost of (very) long-baseline radio interferometers. Realistic intensity interferometer designs are able to achieve limiting R-band magnitudes as good as m~14, sufficient for spatially resolved observations of main-sequence O-type stars in the Magellanic Clouds. Multi-channel intensity interferometers can address a wide variety of science cases: (i) linear radii, effective temperatures, and luminosities of stars; (ii) mass-radius relationships of compact stellar remnants; (iii) stellar rotation; (iv) stellar convection and the interaction of stellar photospheres and magnetic fields; (v) the structure and evolution of multiple stars; (vi) direct measurements of interstellar distances; (vii) the physics of gas accretion onto supermassive black holes; and (viii) calibration of amplitude interferometers by providing a sample of calibrator stars.

In this colloquium, I am going to mainly talk on my recent work on the tidal disruption of stars by supermassive black holes, specifically how accretion disks are formed around spinning supermassive black holes in tidal disruption events. Since I am moving from KASI to CBNU soon, I would also like to talk on how to find evidences for binary supermassive black holes on sub-parsec scales in the context of the binary-disk interaction, which is another topic I have been working on with colleagues in KASI.