Joint Press Release Takeshi Iizuka (Associate Professor, Department of Earth and Planetary Science) Shogo Tachibana (Professor, Department of Earth and Planetary Science, ISAS)
A research group led by Professor Tetsuya Yokoyama of the Department of Earth and Planetary Science, Faculty of Science, Tokyo Institute of Technology, Associate Professor Tsuyoshi Iizuka and Professor Shogo Tachibana of the Graduate School of Science, University of Tokyo, and Professor Hisayoshi Yurimoto of the Graduate School of Science, Hokkaido University has measured the isotopic composition of the Cb-type asteroid Ryugu, and found that intense water metamorphism and water circulation on Ryugu caused local heterogeneity in chromium isotopic composition, They found that local inhomogeneities in chromium isotopic compositions were caused by the intense water metamorphism and water circulation that occurred on Ryugu.
Initial analysis of Ryugu samples revealed that the chemical and mineral compositions of the Cb-type asteroid Ryugu are similar to those of Ivuna-type carbonaceous meteorites, but there is a slight discrepancy between Ryugu and Ivuna-type carbonaceous meteorites in terms of chromium nucleosynthesis origin isotopic anomalies, the cause of which has been awaited to be clarified. The research group has been waiting for the cause of the anomaly to be clarified.
The research group measured nucleosynthetic origin isotope anomalies of chromium (54Cr) and titanium (50Ti) in a total of five Ryugu samples. The results showed that the 54Cr isotopic anomaly varied significantly from higher to lower than the average value for Ivna-type meteorites. This variation is inversely correlated with that of chromium isotopes (53Cr) derived from radiolytic decay of manganese-53 (53Mn), a short-lived nuclide. The 54Cr isotopic anomaly in the combined Ryugu samples (7-24 mg) (about 90 mg) is consistent with the average value for Ivna-type carbonaceous meteorites. In the initial analysis of the Bennu samples brought back by OSIRIS-REx, it was found that it is desirable to analyze a certain amount of sample (>0.1 g) in order to avoid the influence of heterogeneity.
11/10/2023[Press Release] Chromium Isotope Heterogeneity in the Water Cycle of Ryugu Celestial Body -An Important Guideline for Isotope Analysis of Samples Returned from Asteroids はコメントを受け付けていませんNews, UTOPS-News Like
Joint Press Release Kotaro Kono, Professor, Astronomy Education and Research Center)
An international research team led by Assistant Professor Takuma Izumi of the National Astronomical Observatory of Japan (NAOJ) has observed the Compass Galaxy in the nearby universe with the ALMA telescope at an extremely high resolution of about one light year, and succeeded in quantitatively measuring the gas flow and its structure on a spatial scale of only a few light years around a supermassive black hole in all phases: plasma, atomic and molecular. The result was the world’s first successful quantitative measurement of the gas flow and its structure in all phases of plasma, atoms, and molecules. As a result, the accretion flow toward the supermassive black hole was clearly observed, and it was also clarified that the accretion flow is caused by a physical mechanism called “gravitational instability”. Furthermore, it was found that the majority of the accretion flow is not used for the growth of the black hole, but is instead ejected as atomic or molecular gas from the vicinity of the black hole, and then returns to the gas disk to become accretion flow to the black hole again, as if a fountain-like gas cycle is taking place. This is an important achievement toward a comprehensive understanding of the growth mechanism of supermassive black holes.
These observation results were published in the American journal Science on November 3, 2023 as “Supermassive black hole feeding and feedback observed on sub-parsec scales” by Izumi et al. (DOI: 10.1126/science.adf0569).
Figure: The center of the Compass Galaxy as observed by ALMA. The distribution of carbon monoxide (CO) reflecting medium density molecular gas is shown in red, carbon atoms (C) reflecting atomic gas in blue, hydrogen cyanide (HCN) reflecting high density molecular gas in green, and hydrogen recombination lines (H36α) reflecting plasma gas in pink. The active galactic nucleus is located in the center of the figure. This galaxy is known to have an inclined structure from the outer to the inner part, and at the center it approaches the shape of a high-density molecular gas disk viewed from the side. This high-density molecular gas disk (the green region in the center of the figure; see also the zoom in the upper right) is about 6 light years in diameter and was clearly seen for the first time with the high resolution of ALMA’s telescope. The plasma jet stream is almost perpendicular to this dense molecular gas disk. Credit: ALMA (ESO/NAOJ/NRAO), T. Izumi et al.
Professor Kotaro Kono of the Center for Astronomy Education and Research is participating in this research.
For more information, please visit the website of NAOJ and NAOJ ALMA Project.
11/03/2023[Press Release] Finally Unraveled! Growth Mechanism of Supermassive Black Holes and Material Circulation in the Galactic Center はコメントを受け付けていませんNews, UTOPS-News Like
Joint Press Release Satoshi Kasahara (Associate Professor, Department of Earth and Planetary Science)
Professor Lynn Kistler, Professor Yoshizumi Miyoshi, and Project Associate Professor Tomoaki Hori of Nagoya University and their colleagues, Associate Professor Kazushi Asamura and Professor Iku Shinohara of the Japan Aerospace Exploration Agency, Associate Professor Satoshi Kasahara and Assistant Professor Kunihiro Keika of the University of Tokyo, and Associate Professor Shoichiro Yokota of Osaka University, and their colleagues in the United States discovered that the main cause of space storms is plasma originating from the Earth, rather than plasma originating from the Sun as previously thought.
Through international collaboration, the research team analyzed data from a total of four scientific satellites, including the Japanese Geospace Exploration Satellite Arase, NASA of the United States, and ESA of Europe. As a result, they succeeded for the first time in separating the composition of solar- and terrestrial-origin plasma in near-Earth space (geospace), and discovered that the plasma in the Earth’s magnetosphere changes from solar to terrestrial origin during space storms. They also identified that the Earth-origin hydrogen ions are initially dominant in the development of space storms, and that the Earth-origin oxygen ions later become the main cause of space storms.
This indicates that not only ions of solar origin, as previously thought, but also those of terrestrial origin influence the development of space storms. During space storms, the space environment around the Earth changes drastically, which can cause disturbances to satellites and strong electric currents on the ground, which can affect the power grid. This research indicates that an accurate understanding of the behavior of not only plasma from the sun but also from the earth is necessary to understand the changes in the space environment caused by space storms and to predict space storms, which will force a major change in the conventional understanding of space storms.
The research results were published in the British scientific journal Nature Communications on October 30, 2023, at 7:00 p.m. CST.
11/01/2023[Press Release] Earth-Originated Plasma is Responsible for the Development of Space Storms ～Discovery by the Arase Satellite Reverses Conventional Theory: Earth-Originated Plasma is Responsible for the Development of Space Storms はコメントを受け付けていませんNews, UTOPS-News Like
Supernovae, exploding stars, play a critical role in the formation and evolution of galaxies. However, key aspects of them are notoriously difficult to simulate accurately in reasonably short amounts of time. For the first time, a team of researchers, including those from The University of Tokyo, apply deep learning to the problem of supernova simulation. Their approach can speed up the simulation of supernovae, and therefore of galaxy formation and evolution as well. These simulations include the evolution of the chemistry which led to life.
When you hear about deep learning, you might think of the latest app that sprung up this week to do something clever with images or generate humanlike text. Deep learning might be responsible for some behind-the-scenes aspects of such things, but it’s also used extensively in different fields of research. Recently, a team at a tech event called a hackathon applied deep learning to weather forecasting. It proved quite effective, and this got doctoral student Keiya Hirashima from the University of Tokyo’s Department of Astronomy thinking.
“Weather is a very complex phenomenon but ultimately it boils down to fluid dynamics calculations,” said Hirashima. “So, I wondered if we could modify deep learning models used for weather forecasting and apply them to another fluid system, but one that exists on a vastly larger scale and which we lack direct access to: my field of research, supernova explosions.”
Supernovae occur when suitably massive stars burn through most of their fuel and collapse in enormous explosions. They are so huge that they can, and do, influence large areas inside their host galaxies. If a supernova had happened a few hundred years ago within a few hundred light-years from Earth, you might not be reading this article right now. So, the better we understand supernovae, the better we can understand why galaxies are the way they are.
“The problem is the time it takes to calculate the way supernovae explode. Currently, many models of galaxies over long time spans simplify things by pretending supernovae explode in a perfectly spherical fashion, as this is relatively easy to calculate,” said Hirashima. “However, in reality, they are quite asymmetric. Some regions of the shell of material that forms the boundary of the explosion are more complex than others. We applied deep learning to help ascertain which parts of the explosion require more, or less, attention during a simulation to ensure the best accuracy, whilst also taking the least amount of time overall. This way of dividing a problem is called Hamiltonian splitting. Our new model, 3D-MIM, can reduce the number of computational steps in the calculation of 100,000 years of supernova evolution by 99%. So, I think we’ll really help reduce a bottleneck too.”
Of course, deep learning requires deep training. Hirashima and his team had to run hundreds of simulations taking millions of hours of computer time (supercomputers are highly parallel, so this length of time would be divided amongst the thousands of computing elements required). But their results proved it was worth it. They now hope to apply their methodology to other areas of astrophysics; for example, galactic evolution is also influenced by large star-forming regions. 3D-MIM models the deaths of stars, and perhaps soon it will be used to model their births as well. It could even find use beyond astrophysics altogether in other fields requiring high spatial and temporal resolutions, such as climate and earthquake simulations.
Papers
Keiya Hirashima, Kana Moriwaki, Michiko S. Fujii, Yutaka Hirai, Takayuki R. Saitoh, and Junichiro Makino, “3D-Spatiotemporal Forecasting the Expansion of Supernova Shells Using Deep Learning toward High-Resolution Galaxy Simulations,” Monthly Notices of the Royal Astronomical Society: October 23, 2023, doi:10.1093/mnras/stad2864. Link (Publication)
10/23/2023[Press Release] Deep learning speeds up galactic calculations A new way to simulate supernovae may help shed light on our cosmic origins はコメントを受け付けていませんNews, UTOPS-News Like
Fast radio bursts, or FRBs, are an astronomical mystery, with their exact cause and origins still unconfirmed. These intense bursts of radio energy are invisible to the human eye, but show up brightly on radio telescopes. Previous studies have noted broad similarities between the energy distribution of repeat FRBs, and that of earthquakes and solar flares. However, new research at the University of Tokyo has looked at the time and energy of FRBs and found distinct differences between FRBs and solar flares, but several notable similarities between FRBs and earthquakes. This supports the theory that FRBs are caused by “starquakes” on the surface of neutron stars. This discovery could help us better understand earthquakes, the behavior of high-density matter and aspects of nuclear physics.
The vastness of space holds many mysteries. While some people dream of boldly going where no one has gone before, there is a lot we can learn from the comfort of Earth. Thanks to technological advances, we can explore the surface of Mars, marvel at Saturn’s rings and pick up mysterious signals from deep space. Fast radio bursts are hugely powerful, bright bursts of energy which are visible on radio waves. First discovered in 2007, these bursts can travel billions of light years but typically last mere thousandths of a second. It has been estimated that as many as 10,000 FRBs may happen every day if we could observe the whole sky. While the sources of most bursts detected so far appear to emit a one-off event, there are about 50 FRB sources which emit bursts repeatedly.
The cause of FRBs is unknown, but some ideas have been put forward, including that they might even be alien in origin. However, the current prevailing theory is that at least some FRBs are emitted by neutron stars. These stars form when a supergiant star collapses, going from eight times the mass of our sun (on average) to a superdense core only 20-40 kilometers across. Magnetars are neutron stars with extremely strong magnetic fields, and these have been observed to emit FRBs.
“It was theoretically considered that the surface of a magnetar could be experiencing a starquake, an energy release similar to earthquakes on Earth,” said Professor Tomonori Totani from the Department of Astronomy at the Graduate School of Science. “Recent observational advances have led to the detection of thousands more FRBs, so we took the opportunity to compare the now large statistical data sets available for FRBs with data from earthquakes and solar flares, to explore possible similarities.”
So far, statistical analysis of FRBs has focused on the distribution of wait times between two successive bursts. However, Totani and co-author Yuya Tsuzuki, a graduate student in the same department, point out that calculating only the wait-time distribution does not take into account correlations that might exist across other bursts. So the team decided to calculate correlation across two-dimensional space, analyzing the time and emission energy of nearly 7,000 bursts from three different repeater FRB sources. They then applied the same method to examine the time-energy correlation of earthquakes (using data from Japan) and of solar flares (using records from the Hinode international mission to study the sun), and compared the results of all three phenomena.
Receiver of the Arecibo Telescope, Puerto Rico. FRB data was provided by the Five-hundred-meter Aperture Spherical Telescope (FAST) in China and the Arecibo Telescope in Puerto Rico, two of the largest single-dish telescopes in the world. Unfortunately, the Arecibo Telescope was damaged and subsequently decommissioned in 2020.
Totani and Tsuzuki were surprised that, in contrast to other studies, their analysis showed a striking similarity between FRBs and earthquake data, but a distinct difference between FRBs and solar flares. Totani explained: “The results show notable similarities between FRBs and earthquakes in the following ways: First, the probability of an aftershock occurring for a single event is 10-50%; second, the aftershock occurrence rate decreases with time, as a power of time; third, the aftershock rate is always constant even if the FRB-earthquake activity (mean rate) changes significantly; and fourth, there is no correlation between the energies of the main shock and its aftershock.”
This strongly suggests the existence of a solid crust on the surface of neutron stars, and that starquakes suddenly occurring on these crusts releases huge amounts of energy which we see as FRBs. The team intends to continue analyzing new data on FRBs, to verify that the similarities they have found are universal. “By studying starquakes on distant ultradense stars, which are completely different environments from Earth, we may gain new insights into earthquakes,” said Totani. “The interior of a neutron star is the densest place in the universe, comparable to that of the interior of an atomic nucleus. Starquakes in neutron stars have opened up the possibility of gaining new insights into very high-density matter and the fundamental laws of nuclear physics.”
Papers
Tomonori Totani and Yuya Tsuzuki, “Fast radio bursts trigger aftershocks resembling earthquakes, but not solar flares,” Monthly Notices of the Royal Astronomical Society: October 11, 2023, doi:10.1093/mnras/stad2532. Link (Publication)
10/12/2023[Press Release] “Starquakes” could explain mystery signals Fast radio bursts from distant neutron stars resemble earthquakes rather than solar flares はコメントを受け付けていませんNews, UTOPS-News Like
Joint Press Release Shogo Tachibana, Professor, Department of Earth and Planetary Science, Space and Planetary Science Organization
Moe Matsuoka, a researcher at the National Institute of Advanced Industrial Science and Technology (AIST) and Toru Kouyama, a team leader, National Institute of Advanced Industrial Science and Technology, in collaboration with Prof. Tomoki Nakamura, Tohoku University; Kana Amano, Japan Society for the Promotion of Science Research Fellow, Tohoku University; Dr. Takahito Osawa, Research Director, Japan Atomic Energy Agency; Prof. Shogo Tachibana, University of Tokyo; Prof. Hiroshi Naraoka and Associate Prof. Takashi Okazaki, Kyushu University, etc. and other researchers, conducted a direct comparison between the data obtained by the asteroid probe Hayabusa2 from the sky over the surface of the asteroid Ryugu and the data obtained by measuring samples collected and brought back (sample return) from Ryugu without exposing them to the Earth’s atmosphere.
As a result, we found that while the observed data from Ryugu’s surface and the sample return data agree well, there is a clear difference in the absorption of hydroxy groups (-OH), which is the key to determine the presence of water. In order to clarify the cause of this difference, experiments and data analysis of primitive meteorites similar to Ryugu, which are rich in hydrous silicates, revealed that Ryugu’s surface (about 1/100 mm) has been altered (space weathering) by exposure to cosmic rays and dust, resulting in partial loss of water.
This research result, which was only possible through a combination of remote observation from the spacecraft and analysis of collected samples, is one of the landmark results that demonstrate the importance of sample return in planetary exploration. The details of the study were published in Communications Earth & Environment on September 27, 2023 (JST).
For more information, please refer to the following
10/03/2023[Press Release] Why Does Asteroid Ryugu Look Different in Space and in the Laboratory? ~Space Weathering Hides the Signs of Water はコメントを受け付けていませんNews, UTOPS-News Like
Tomo-e Gozen camera (https://tomoe.mtk.ioa.s.u-tokyo.ac.jp) on the 1.05 m Kiso Schmidt telescope, Univ. Tokyo, successfully filmed the OSIRIS-REx spacecraft and the Sample Return Capsule!
09/25/2023Tomo-e Gozen Camera at the UTokyo Kiso Observatory Successfully Filmed the OSIRIS-REx Spacecraft and the Sample Return Capsule はコメントを受け付けていませんNews, UTOPS-News Like
Joint Press Release Shogo Tachibana (Professor, Department of Earth and Planetary Science, Japan Aerospace Exploration Agency)
Japan Agency for Marine-Earth Science and Technology (JAMSTEC; President: Hiroyuki Yamato) The international collaborative research group led by Dr. Toshihiro Yoshimura, Deputy Senior Researcher, and Dr. Yoshinori Takano, Senior Researcher, at the Biogeochemistry Research Center, and Prof. Hiroshi Naraoka, Graduate School of Science, Kyushu University, is a joint research group with the Graduate School of Science, The University of Tokyo, National Institute of Advanced Industrial Science and Technology (AIST), Horiba Advanced Techno Co. The group, together with researchers from the Graduate School of Science at the University of Tokyo, National Institute of Advanced Industrial Science and Technology, Horiba Techno, Horiba Techno Service, Thermo Fisher Scientific Japan Group, Hokkaido University, and Tokyo Institute of Technology, conducted precise chemical analysis of soluble components in samples from the asteroid Ryugu to determine their composition, content, etc. The results of the analysis are shown in Table 1. The composition and content of the soluble components were clarified.
Asteroid Ryugu is one of the primordial bodies that retain the chemical composition of the entire solar system before the birth of the Earth. The initial analysis of Hayabusa2 has revealed various properties, contents, and history of the asteroid, but the material information of ionic components among soluble components has remained unknown.
In this study, soluble components were extracted from samples of the asteroid Ryugu and precisely analyzed at the inorganic and organic molecular levels. The results showed that hydrothermal extracts, which reflect the most soluble components, are very rich in sodium ions (Na+). Sodium ions act as electrolytes that stabilize the surface charge of minerals and organic matter, and some are thought to precipitate as sodium salts (Salt) by binding with organic molecules and other substances. Various organosulfur molecules were also found in the extract. It is thought that the chemical state of the organic sulfur molecules in the water on the asteroid Ryugu changed, resulting in the chemical evolution of a wide variety of organosulfur molecules.
This finding is important not only for unraveling the material evolution of the early solar system, but also for answering the major question of how they led to the chemical processes that ultimately led to the birth of life.
The results were published in the scientific journal Nature Communications on September 18, 2023 (JST).
