Release

New Proof for Black Hole Spin

The nearby radio galaxy M87, located 55 million light-years from the Earth and harboring a black hole 6.5 billion times more massive than the Sun, has recently been discovered to exhibit an oscillating jet. This investigation found the jet swinging up and down with an amplitude of about 10 degrees. Through the extensive analysis of data observed from 2000 to 2022 by various international networks of radio telescopes, the research team unveils a recurring 11-year cycle in the precessing motion of the jet base, as predicted by Einstein’s general relativity. This work successfully linked the dynamics of the jet with the central supermassive black hole, offering the evidence for the existence of M87’s black hole spin. The work is published in the current issue of Nature.

Triple Baby Stars Reach Out Three Arms to Feed with Materials

An international research team led by Jeong-Eun Lee, a professor at Seoul National University, used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the triple protostar system IRAS 04239+2436, to investigate the detailed structure of the gas around the protostars. As a result, they detected radio waves emitted by sulfur monoxide (SO) molecules that indicate the presence of shockwaves and discovered that their distribution forms three large spiral arms. By comparing the velocity of the gas obtained from the observations with numerical simulations led by Tomoaki Matsumoto, a professor at Hosei University, they found that the three spiral arms also play a role of “streamers” feeding materials to the three protostars. Although the origin of the streamers has been unclear, the combination of observations and simulations reveals, for the first time, how the streamers form in the dynamical process of multiple star formation.
This research was presented in a paper "Triple spiral arms of a triple protostar system imaged in molecular lines" by Jeong-Eun Lee et al. in the Astrophysical Journal on August 4, 2023. (August 4, 2023 Press Release)

Out of this World Control on Ice Age Cycles

A research team, composed of climatologists and an astronomer, have used an improved computer model to reproduce the cycle of ice ages (glacial periods) 1.6 to 1.2 million years ago. The results show that the glacial cycle was driven primarily by astronomical forces in quite a different way than it works in the modern age. These results will help us to better understand the past, present, and future of ice sheets and the Earth’s climate. (May 15, 2023 press release)

Rare Earth Element Synthesis Confirmed in Neutron Star Mergers

A research group led by Nanae Domoto, a graduate student at the Graduate School of Science at Tohoku University and a research fellow at the Japan Society for the Promotion of Science (JSPS), has systematically studied the spectra from this kilonova—bright emissions caused by the radioactive decay of freshly synthesized nuclei that were ejected during the GW170817 merger. Based on comparisons with detailed simulations of kilonova spectra produced by the supercomputer “ATERUI II” at the National Astronomical Observatory of Japan, the team found that the rare earth elements lanthanum and cerium can reproduce the near-infrared spectral features seen in 2017. (October 27, 2022 press release)

Massive Stars Moving around in Star Clusters

A research group at the University of Tokyo has performed a simulation of star cluster formation using a newly developed simulation code. The simulation revealed that some massive stars formed in the star cluster center were ejected to the outskirts of the cluster and ionized the molecular cloud there. These processes caused the formation of off-centered ionized bubbles seen in the Orion Nebula.

Stellar “Ashfall” Could Help Distant Planets Grow

The world’s first 3D simulation simultaneously considering dust motion and growth in a disk around a young star has shown that large dust from the central region can be entrained by and then ejected by gas outflows, and eventually fall back onto the outer regions of the disk where it may enable planetesimal formation. This process can be likened to volcanic “ashfall” where ash carried up by gas during an eruption falls back on the area around the volcano. These results help to explain observed dust structures around young protostars.

Simulations Provide Clue to Missing Planets Mystery

Forming planets are one possible explanation for the rings and gaps observed in disks of gas and dust around young stars. But this theory has trouble explaining why it is rare to find planets associated with rings. New supercomputer simulations show that after creating a ring, a planet can move away and leave the ring behind. Not only does this bolster the planet theory for ring formation, the simulations show that a migrating planet can produce a variety of patterns matching those actually observed in disks.