国立天文台　セミナー情報　/　Seminar Information

2021.11.29-2021.12.5

2021-11-26 (金)
太陽系小天体セミナー | 科学研究部コロキウム

Nov 30 Tue 10:00～11:30　太陽系小天体セミナー / Solar System Minor Body Seminar　 zoom

Dec 1 Wed 15:30～17:00　 NAOJ Science Colloquium zoom

詳細は以下をご覧下さい

11月30日（火）

キャンパス：三鷹
セミナー名：太陽系小天体セミナー
定例・臨時の別：定例
日時：11月30日（火曜日）10時00分～11時30分
場所：zoom

世話人の連絡先
　名前：渡部潤一
備考：テレビ会議またはスカイプによる参加も可

12月1日（水）

Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2021 Dec 1, 15:30-17:00
Place：zoom
Speaker：Fabian Schneider
Affiliation：HITS gGmbH
Title：Turbulent Lives of Stars
Abstract：Stars are the basic building blocks of the visible Universe. Understanding how they transformed the pristine Universe into the one we live in today is at the heart of astrophysical research and vital for many areas in astrophysics. For example, massive stars are cosmic powerhouses and their immense radiation, strong stellar winds and powerful supernova explosions helped to re-ionise the Universe after the Dark Ages, drive the evolution of galaxies and laid the foundation for life as we know it. At the end of their lives, stars produce compact objects whose mergers are now routinely observed thanks to gravitational-wave observatories. Yet, our understanding of the lives and final fates of stars is seriously incomplete. I will review some pressing challenges in stellar astrophysics with a particular emphasis on massive binary stars. In binary systems, stars can exchange mass, thereby completely changing their evolution and final fates. Stripping off the envelope of a massive star may allow it to explode in a supernova and produce a neutron star instead of collapsing into a black hole. In many cases, binary mass transfer results in stellar mergers and common-envelope episodes. I will present simulations that show the emergence of strong magnetic fields in such dynamic and turbulent phases with possibly far-reaching consequences. Merged stars may be highly magnetic and the progenitors of the strongest magnets in the Universe, so-called magnetars. In common-envelope episodes, the magnetic fields can drive bipolar, jet-like outflows and may help explain the shapes of asymmetric planetary nebulae.
Facilitator
-Name：Akimasa Kataoka
Comment：English

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2021.11.22-2021.11.28

2021-11-19 (金)
Solar and Space Plasma (SSP) Seminar | 科学研究部コロキウム

Nov 24 Wed 15:30～17:00　 NAOJ Science Colloquium 　　　　　　　　　　 zoom

Nov 26 Fri 13:30～15:00 　 Solar and Space Plasma Seminar 　　　　　　　　　　 zoom

詳細は以下をご覧下さい

11月24日（水）

Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2021 Nov. 24, 15:30-17:00
Place：zoom
Speaker：Takemura Hideaki
Affiliation：D2
Title：The possibility of core growth with mass accretion and the core mass calculation method for continuum observations
Abstract：Stars are formed in dense regions which are called dense cores in the molecular clouds. Thus, it is crucial to understand how dense cores form from parental molecular clouds to reveal star formation processes. Since the evolution process of a star strongly depends on the mass, the mass is one of the most important properties of a dense core as well. The mass functions of dense cores (CMFs), the mass spectrum of dense cores, are expected to have information of the core evolution and star formation processes. Many previous studies of CMFs toward nearby star-forming regions with single-dish telescopes have suggested that the CMFs resemble the stellar IMFs. However, top-heavy CMFs are reported from recent ALMA observations toward distant high-mass star-forming regions. Therefore, the processes that link CMF and IMF have not been revealed. In this presentation, I will discuss the possibility of core growth suggested from the comparison of CMF and IMF in the Orion Nebula Cluster region and the core mass calculation method for dust continuum observation of ALMA.

Speaker：Kashiwagi Raiga
Affiliation：D1
Title：The Role of Filament-Filament Collision in Star Formation
Abstract：Filamentary structures are recognized as a fundamental component of interstellar molecular clouds in observations made by the Herschel satellite. In addition, most of the prestellar cores that will become protostars in the future have been found along gravitationally unstable filaments. Based on these observational results, the relationship between filaments and star formation has attracted much attention. Recently, some observations imply that star formation is caused by filament-filament collisions. However, theoretical predictions are still insufficient: how they will evolve and which physical parameters change their evolution. Thus, We are challenging the theoretical understanding of filament-filament collisions by using numerical calculation. In this seminar, I will report the first result of a 2d-hydrodynamical simulation that investigated evolutions of filament-filament collisions and what parameters controlled their evolution.

Facilitator
-Name：Akimasa Kataoka
Comment：English,

11月26日（金）

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：26 November (Fri), 13:30-15:00
Place： zoom
Speaker：正木寛之
Affiliation：千葉大学
Title：数値シミュレーションと機械学習を組み合わせた太陽表面の速度場・磁場推定
太陽の放射強度、視線方向磁場、視線方向速度場のスナップショットを用いて
太陽表面の水平速度場、水平磁場を予測するニューラルネットワークを開発した。
太陽ではこれまでに高精度な望遠鏡、衛星を用いた多くの観測が行われている。
しかし観測精度が十分でない物理量や、原理上、直接観測できないものなどもあり
すべての太陽のデータを得ることはできない。そこで本研究ではシミュレーションと
ディープラーニングを組み合わせることにより、このような観測が難しい物理量を
人工知能の高い推測能力によって放射強度など観測が容易な物理量から評価する手法を開発した。
現在までに太陽表面での水平速度場と水平磁場の予測を行っており、
シミュレーションデータとネットワークの推定したデータとの間の相関係数として、
水平速度場では0.7、水平磁場では0.6を達成している。