宇宙科学談話会

ISAS Space Science Colloquium & Space Science Seminar

FY2022

ENGLISH

Observations of weather and climate in giant planet upper atmospheres

Dr. James O'Donoghue
ISAS/JAXA Dept. of Solar System Sciences

At Jupiter and Saturn, magnetosphere-ionosphere coupling gives rise to intense auroral emissions and enormous energy deposition in the magnetic polar regions. At Jupiter, we found that temperatures decrease steadily from the auroral polar regions to the equator, indicating that the aurora act as a planet-wide heating source. On top of this, during a period of enhanced activity in Jupiter's auroral region, a high-temperature planetary-scale-sized structure was also observed to traveling toward the equator from the poles. This presentation reports on the particulars of this feature, including how it appears to be propagating away from the auroral region (as determined by estimates of the features' velocity at several longitudes) and its implications for global energy circulation at Jupiter and other planets. In general, these are our first glimpses into both climate and weather in Jupiter's upper atmosphere. I will also discuss our plans to follow-up on this study with new Keck data recorded in FY2022. At Saturn, the rings dominate the non-auroral conditions around the planet via a mechanism called 'ring rain'. Electrically charged material rains onto the planet, leaving a signal in the upper atmospheric emissions measured from ground-based telescopes like Keck. I will discuss how we will examine new JWST data, which has exquisite sensitivity, to learn more about the ring rain phenomenon, and show how it is important for determining the erosion rate, hence the lifetime, of Saturn's rings.

Via Zoom / Zoom 開催

ENGLISH

Planet Formation Theory ⨉ Planetary Exploration

Dr. Ryuki Hyodo
ISAS/JAXA Dept. of Solar System Sciences

In this talk, I will present my recent research projects regarding planet formation and planetary explorations. These include MMX, Hayabusa2, Hera, planetesimal formation, rings of Saturn, etc.

Via Zoom / Zoom 開催

日本語

小望遠鏡動画観測が解明する太陽系の影と閃光

有松 亘(ありまつ こう)
京都大学 白眉センター

口径0.28mの小型観測装置を用いながら、外部太陽系の小天体に関する新たな知見をもたらす2つの観測プロジェクト、OASESとPONCOTSについて紹介する。OASES(Organized Autotelescopes for Serendipitous Event Survey)は未知の太陽系外縁天体による恒星掩蔽現象の検出を目的として、沖縄県宮古島市にて小望遠鏡2台を用いて実施した可視動画モニタ観測プロジェクトである。2016年から2017年にかけて実施したOASESモニタ観測により、キロメートルサイズの太陽系外縁天体による恒星掩蔽イベント候補の検出に史上初めて成功した。このOASESの観測成果は太陽系外縁部の新たな知見を与えただけでなく、本プロジェクトが題材になった小説(オオルリ流星群, 伊与原 新 著, KADOKAWA)が刊行されるなど、一般社会にもインパクトをもたらした。
PONCOTS(Planetary ObservatioN Camera for Optical Transient Surveys)は、新型コロナウイルスの感染拡大によってOASESプロジェクトが休止して暇になったことに伴い、2021年9月に京都大学吉田キャンパス施設屋上で開始した木星動画モニタ観測プログラムである。2021年10月15日にはこのPONCOTSプログラムによって、史上9例目となる未知小天体の木星衝突に伴う閃光イベントを発見した。PONCOTS観測システムはこの木星閃光の3波長同時動画観測に史上初めて成功し、閃光の波長特性や衝突天体の質量・サイズを明らかにした。本談話会ではOASESとPONCOTSのこれまでの経緯と成果、今後の所期を概括する。

A2F Conference hall(1236),Via Zoom / Zoom 開催

ENGLISH

The role of the NASA's New Frontiers Program and Comet Surface Sample Return in Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032.

Prof. Alexander Hayes(アレクサンダー・ヘイズ教授)Mr. Michael Amato(マイケル・アマト主任エンジニア)
Cornell UniversityGoddard Space Flight Center NASA

Origins, Worlds, and Life (OWL): A Decadal Strategy for Planetary Science and Astrobiology 2023-2032 highlights key science questions, identifies priority missions, and recommends a comprehensive research strategy for NASA's next decade of planetary science and astrobiology investigations. New research will expand our understanding of our solar systems origins, how planets form and evolve, under what conditions life can survive, and where to find potentially habitable environments in our solar system, and beyond. This seminar will provide a broad overview of OWL's recommendations, and then highlight the role of NASA's competitive New Frontiers (NF) program and sample science, including the role of Comet Surface Sample Return, in completing the objectives outlined in OWL.

A2F Conference hall(1236),Via Zoom / Zoom 開催

日本語

JASMINE計画の誕生と変遷

Dr. 郷田 直輝(ごうだ なおてる)
国立天文台

JASMINE(JAXA宇宙科学研究所の公募型小型計画3号機)は、光学望遠鏡(主鏡口径36cm程度)と開発中の国産宇宙用赤外線検出器を用いて、赤外線位置天文観測で星の距離と運動を測定することにより、天の川銀河形成の鍵を握る中心核領域にある構造(中心核構造)を明らかにすることを科学目標の1つにしています。可視光では塵にさえぎられて観測しにくい天の川銀河の中心核領域を赤外線で測定し、中心核構造とその形成史や巨大ブラックホールの進化を明らかにすること(銀河中心考古学)を大きな目標としています。また、位置天文観測で達成される高精度な測光能力を活かしたトランジット観測により、中期M型星周りの生命居住可能領域にある地球型惑星を探査することも大きな科学目標です。先ずは、このようなJASMINEの全体的な概要と状況を説明します。
さらに、位置天文観測の歴史、JASMINE計画が立ち上がった背景と経緯(なぜ位置天文学の"素人"がJASMINEをやろうと思ったか等)、その後の長年に亘るJASMIN計画の様々な変遷(超小型と大中小計画)について、いくつかのエピソードを交えながら紹介させていただきます。

A2F Conference hall(1236),Via Zoom / Zoom 開催

ENGLISH

NASA Space Science - Carpe Posterum: Achievements and Future Plans

Dr. Thomas Zurbuchen, Dr. Mark Clampin
NASA

NASA's Science Mission Directorate vision is leading discovery, seeking new knowledge and understanding of our planet Earth, our Sun and solar system, the universe out to its farthest reaches and back to its earliest moments of existence, and enabling space exploration as well as benefits for life on Earth. NASA Associate Administrator for Science, Dr. Thomas Zurbuchen, and Dr. Mark Clampin, NASA's Astrophysics Program Director, will talk about achieving this vision through recent science accomplishments and future plans in NASA's Planetary Science, Planetary Defense, Heliophysics and Astrophysics programs.

A 2F Conf. room(1236) / 研究管理棟2階会議場(1236号室)、Via Zoom / Zoom 開催

ENGLISH

Missions to Binary Asteroids: A Pathway to Understanding the Morphological Evolution of Rubble Pile Asteroids

Prof. Daniel J. Scheeres (ダニエル・シアーズ教授)
Ann and H.J. Smead Department of Aerospace Engineering Sciences, The University of Colorado at Boulder

Binary asteroids are found frequently within the small Near Earth Asteroid (NEA) population, with about 15% of all asteroids believed to be binaries. However, there are reasons to believe that the processes that create binary asteroids are the same that drive the overall evolution of small rubble pile asteroid morphologies. In this talk we will outline how the processes that create binary asteroids should shape many other aspects of the small asteroid population. Motivated by this, it becomes clear that missions which explore binary asteroids to determine the details of their formation processes may also provide insight and understanding on the overall evolution of the small body population in the solar system. We will introduce a few planned missions to binary asteroids that will investigate these bodies in detail for the first time. Beyond these planned missions there are also many other possible approaches to exploring binary asteroids that could further unveil the formation mechanics of these systems, and hence shed insight on the small body population.

A1F Entrance hall, Via Zoom / Zoom 開催

※ 通常と曜日が異なりますので、ご注意下さい。

ENGLISH

Mapping Solar Magnetic Fields by Sounding Rocket Experiments CLASP2 and CLASP2.1

ISHIKAWA Ryohko (石川 遼子)
National Astronomical Observatory of Japan

The magnetic field measurements in the solar chromosphere and above are critical to understand the solar activities in the corona as well as in the chromosphere. To this end, we need to measure and model the polarization of ultraviolet (UV) spectral lines originating in the chromosphere, which encodes the information on the magnetic fields. The Chromospheric LAyer Spectro-Polarimeter (CLASP2) sounding rocket experiment was carried out on 2019 April 11, providing the first ever spectrally and spatially resolved Stokes profiles (intensity, linear polarization, and circular polarization) across the Mg II h & k lines at 280 nm. We demonstrated the presence of the scattering polarization and the operation of the Hanle and Magneto-Optical effects over the Mg II h & k lines. Moreover, through coordinated observations with the Solar Optical Telescope (SOT) aboard the Hinode satellite, we have shown how the magnetic fields expand with height in the chromosphere of the active region, coupling the different atmospheric layers. To further demonstrate the maturity of the UV spectropolarimetry techniques, on 2021 October 8, we re-flew the CLASP2 payload with a modified observing program to produce a multi-height, two-dimensional map of the chromospheric magnetic field as CLASP2.1. In this talk, we summarize the scientific results of the CLASP2 and CLASP2.1 and the perspectives for the future.

Via Zoom / Zoom 開催

※ 通常と曜日・時間が異なりますので、ご注意下さい。

ENGLISH

Low-latency detection of the gravitational waves from compact binary coalescences

TSUKADA Leo(塚田 怜央)
The Pennsylvania state university, Postdoctoral Scholar

Since the first detection of the gravitational wave from a binary black hole, the LIGO-Virgo-KAGRA (LVK) collaboration has detected in total 90 events from compact binary coalescences, establishing the field of gravitational wave astronomy. In addition to shedding light on the properties of compact objects e.g. black holes and neutron stars, the joint observation of such objects together with electromagnetic emission will bring us further enriched insight on nuclear physics and cosmology. Early 2023, the forth observing run is going to take place and various methods have been extensively developed towards it. Today, I will talk about methods to detect gravitational waves in low latency, which plays a crucial role in so-called multi-messenger astronomy. In particular, this talk will be focused on the methodology of a low-latency detection pipeline, GstLAL. GstLAL can also incorporate the detection method with negative latency, i.e. early warning. I will briefly describe its prospect in the upcoming forth observing run by the LVK collaboration.

A 2F Conf. room(1236) / 研究管理棟2階会議場(1236号室)、Via Zoom / Zoom 開催

日本語

EHTCのM87ブラックホールの「リング」像は本物か? ─ 観測データの独立解析の結果 ─

三好 真(ミヨシ マコト)
国立天文台

小田稔が「はくちょう座X-1」のX線観測から「ブラックホール」である可能性を言及したことから始まった観測的ブラックホール研究は今や興隆を極め、2020年には天の川銀河系中心の大質量ブラックホールの存在検証に対してノーベル物理学賞が与えられるまでになった。
そのなかでVLBIを用いて「ブラックホールを見る」観測が検討され、早くも2019年にその成功がEHTC(Event Horizon Telescope Collaboration;EHTC)から報告された。EHTCの報告した銀河M87の大質量ブラックホール像として直径42μasのリング像の大きさであったが、これは推定60億太陽質量から相対性理論によって予想されるシャドーサイズと一致していた。
ところが、このリングサイズは同時にEHTのPSF(point spread function)に現われる凹凸の間隔とも一致することに講演者らは気がつき、独自のデータ解析を始めた。EHTCの報告したリング像はM87の天体像ではなく、PSFの特徴、つまり望遠鏡の光学系のくせを取り込んで合成してしまったものだと結論した。講演者らは独自に像合成も行い、M87の宇宙ジェットに関わる構造も見いだしている。講演では、どちらがより正しい像であるか客観的事実から示してゆきたい。
時間があればEHTCが最近発表した天の川銀河系中心のブラックホール像についても言及し、スペースや月面からの観測の可能性も含め、よりよい「ブラックホールを見る」観測装置に関する提案も行いたい。

研究管理棟2階会議場(1236号室)、Zoom 開催

ENGLISH

Measurements of the Cosmic Microwave Background polarisation: from Planck to LiteBIRD

Guillaume Patanchon(ギョウム パタンチョ)
Astroparticle and cosmology laboratory (APC), France

The small fluctuations of the Cosmic Microwave Background (CMB), that is a radiation from 380000 years after the Big-Bang measured today at the temperature of 2.7 Kelvins, contain a wealth of information about the primordial Universe. The signal is polarised and two types of polarisation patterns on the sky can be produced: the positive parity E modes sourced by density perturbations and a peculiar negative parity polarisation pattern called B-modes. B-modes are expected to be generated by primordial gravitation waves produced during the hypothetical inflation phase of the Universe happening 10^-34 s after the Big-Bang.The Planck satellite provided cosmic variance limited temperature fluctuations over the whole sky and most of the relevant angular scales. This led to percent accuracy measurement of the main cosmological parameters of the standard cosmological model. Planck also provided accurate measurements of E-modes leading to an estimation of the optical depth tau. Planck measurements required understanding many sources of systematic effects coming from the instrument itself, from the satellite environment as well as astrophysical sources, and required intensive data analysis to process them. Polarisation measurement was particularly difficult because it requires differencing measurements taken under different condition on a large intensity background.
LiteBIRD is a satellite mission of JAXA (with the participation of other agencies such as CNES of France) to be launched at the end of 2020's targeting the B-mode signal at large angular scales by measuring the whole sky in 15 different frequency bands with several thousands of detectors (while Planck was using < 100 detectors). This extremely accurate measurement will require the control systematic effects with unprecedented accuracy. After introducing the CMB physics, I will present the Planck results and analysis. I will then review the possible sources of systematics for LiteBIRD and how to handle them.

A 2F Conf. room(1236) / 研究管理棟2階会議場(1236号室)、Via Zoom / Zoom 開催

※ 通常と曜日が異なりますので、ご注意下さい。

ENGLISH

Imaging of the Supermassive Black Hole in Our Galaxy, Sgr A* with the Event Horizon Telescope

2022年7月6日(水) → 2022年7月20日(水)に変更になリました。】

KOFUJI Yutaro(小藤 由太郎)
Department of Astronomy, School of Science, the University of Tokyo/National Astronomical Observatory of Japan(NAOJ)

The first event horizon scale image of the supermassive black hole in our Galaxy, Sgr A* was captured by the Event Horizon Telescope(EHT) Collaboration. EHT is the Very Long Baseline Interferometry (VLBI) that links radio dishes around the world to create an Earth-sized telescope virtually. High-resolution observations of EHT enable us to see the vicinity of the black hole. The obtained image of the black hole shadow is consistent with the prediction of general relativity.
The observations were done in 2017 April at a wavelength of 1.3mm. In the imaging process, we used 4 imaging methods, CLEAN, regularized maximum likelihood (RML) methods, and a Bayesian posterior sampling method. The main challenges of Sgr A* imaging are the rapid time variation and interstellar scattering, and the mitigation processes for these effects are developed. Each imaging method has imaging parameters including these mitigation processes and we performed the parameter survey using ~200 thousand parameter combinations. From these parameters, we choose ~10 thousand "Top Set" parameters that can distinguish different morphologies. The Sgr A* images reconstructed with "Top Set" parameters are clustered into 4 morphologies, 3 ring clusters that have different brightness distributions and a small number of non-ring images. Based on the multiple tests, we conclude that Sgr A* is highly likely to have ~50 micro-arcsecond ring structure. The comparison between the reconstructed images and the theoretical simulations shows that reconstructed images are consistent with the shadow of the Kerr black hole which weighs ~4 million solar masses.

A 2F Conf. room(1236) / 研究管理棟2階会議場(1236号室)、Via Zoom / Zoom 開催

ENGLISH

TMT science cases and the project status

AOKI Wako(青木 和光)
National Astronomical Observatory of Japan(NAOJ)

The Thirty Meter Telescope (TMT) project is an international collaboration of five countries to construct an optical/infrared extremely large telescope. It will achieve more than three times higher resolving power and 100 times higher sensitivity for point sources than the current large telescopes. This will significantly enhance studies of extrasolar planets to enable direct imaging of earth-like planets and determining compositions of their atmospheres that might include signatures of life. TMT will also explore the light from first stars in distant galaxies and determine elements produced by explosions studied by multi-messenger astronomy. The project expects collaborations with space sciences and Solar System missions in 2030s and beyond. The TMT project has been engaging community in Hawaii to have understanding for astronomy and the telescope, having remarkable progress in dialogues in the community. Founding a new management organization involving native Hawaiians was recently approved by Hawaii state legislature. Following the recommendations in the Decadal Survey, NSF will start reviewing process for the US-ELT project including TMT. The status and prospect of the project are presented in this seminar.

A 2F Conf. room(1236) / 研究管理棟2階会議場(1236号室)、Via Zoom / Zoom 開催

ENGLISH

Eruptions from Young Solar-like Stars and Impact of Habitable Environments of Rocky Exoplanets

Vladimir Airapetian
NASA Goddard Space Flight Center and American University

Is life unique to Earth or a common phenomenon in the Solar System and the Universe? This fundamental question is one of the greatest puzzles of modern science. Earth's evident long-term habitability makes it a key data point for understanding the formation of habitable worlds in the Universe. To address this fundamental question, we need to know how the basic requirements for life as we know it such as liquid water, organic compounds and persistent external energy fluxes promoted the emergence and complexification of biological systems on early Earth and how they were impacted by planetary and solar properties. The early Solar System was a chaotic place, likely subject to frequent large impacts as well as the violently changing space weather (energetic ionizing radiation flux from the solar corona, wind and transient events) from the infant (< 100 Myr) and toddler (400-600 Myr) Sun. Understanding the conditions that allowed for the emergence of life on early Earth, and whether other inner planets in our Solar System possibly also supported habitable conditions early in their histories is a promising way to address these questions. Thus, the knowledge of the heliospheric environments surrounding the early Venus, Earth and Mars is critical for evaluation of the basic requirements for life as we know it including liquid water and organic compounds. Here, I will describe recent observations of young solar-like stars and the Sun as inputs for our 3D MHD models of the corona, the wind and transient events (flares, coronal mass ejections and solar energetic particle events) and discuss their impact on atmospheric erosion and chemistry of early Earth. I will use these constrained energy fluxes to describe our recent atmospheric chemistry models impacted by energetic particles from the young solar-like stars and formation and precipitation of biologically relevant molecules on rocky exoplanets. I will then highlight our results of laboratory experiments of proton irradiation of mildly reduced gas mixtures and their implications to the climate, prebiotic chemistry and the rise of habitability in exoplanetary systems.

A 2F Conf. room(1236) / 研究管理棟2階会議場(1236号室)、Via Zoom / Zoom 開催