National Astronomical Observatory of Japan

29/05/2026

Research using multiple supercomputers, including ATERUI III at the National Astronomical Observatory of Japan, has found a possible explanation for the hub-and-spoke pattern seen in some molecular clouds where baby stars are forming. According to the new numerical simulations, if an external shock interacts with magnetic fields which have been warped by the motion of the clouds, gas can be channeled into a shape resembling the spokes on the wheels of a baby carriage.

When parts of molecular clouds become dense enough, they can collapse under self-gravity. As a result of this collapse, the gas in the clouds condenses into protostars which will grow into stars. For this reason, molecular clouds are nicknamed “stellar cradles.” But some of these sites of star formation are more like baby carriages than cradles because they have filaments of gas extending toward a central hub, forming a shape like a spoked wheel.

Researchers from Kyushu University and Nagoya University investigated the possibility that magnetic fields within the clouds might play a role in forming this distinct shape. Using ATERUI III, a dedicated-astronomy supercomputer operated by the National Astronomical Observatory of Japan, they modeled how gas and magnetic fields evolve together over time. The results show that as the cloud collapses under self-gravity, it pulls the magnetic field lines inward, bending them into an hourglass shape. The team then simulated the effects of a disturbance like a shock wave from a nearby supernova remnant or from expanding gas around a massive star. The team found that if this shock hits the curved magnetic field at certain angles, it strengthens parts of the magnetic field, forming invisible channels that guide compressed gas into long, narrow filaments converging toward the center.

The team now plans to conduct more simulations to test whether this mechanism can explain more asymmetric and complex shapes. This will help clarify how the diversity of observed hub-filament systems reflects differences in cloud environments and how such environments shape the formation of massive stars and clusters.

(Image Credit: M. S. N. Kumar, ESA/Herschel, NASA/JPL-Caltech (Spitzer), S. Nozaki, S. Inutsuka)

04/05/2026

Outer Solar System Object Has an Atmosphere But Shouldn’t

A team of professional and amateur Japanese astronomers found evidence for a thin atmosphere around a small body in the outer Solar System. The object is so small that it should not have a sustainable atmosphere, raising questions about when and how the atmosphere formed. Future observations to better characterize the atmosphere will help solve these mysteries.

17/04/2026

The Subaru Telescope Sheds Light on the "Color Mystery" of Jupiter Trojan Asteroids ― Insights from Suprime-Cam's Final Night of Observations ―

Observations conducted with the Subaru Telescope and its first-generation wide-field camera, Suprime-Cam, have revealed new insights into the relationship between the color and size of Jupiter Trojan asteroids. While a bimodal color distribution has been well established for larger Jupiter Trojans, the new study shows that smaller Jupiter Trojans exhibit markedly different behavior. This discovery provides an important clue to understanding the origin and evolution of these enigmatic objects.

08/04/2026

The Solar System’s two largest gas giant planets, Jupiter and Saturn, have extensive but very different families of moons orbiting them. New simulations conducted on the PC cluster at the Center for Computational Astrophysics (CfCA), National Astronomical Observatory of Japan (NAOJ) showed that the planet’s magnetic field plays a role in creating an environment where the new moons can survive and grow, thus shaping the evolution of the system.

Jupiter has more than 100 reported moons, including four large ones (Ganymede, Callisto, Io, and Europa). Saturn has more than 280 reported moons, but only one large one (Titan). So it is a puzzle why Saturn managed to cultivate more moons, but fewer large moons than Jupiter.

A team led by Kyoto University, including researchers from institutes in Japan and China, used the PC cluster at CfCA, NAOJ, to simulate the formation of the moon systems around Jupiter and Saturn. This simulation recreated the planets’ internal structure to calculate the thermal evolution of Jupiter and Saturn and how their magnetic fields have varied over time.

Moons form from material in a “circumplanetary disk” of gas and dust orbiting the young planet. The disk nurtures the young moons, but interactions with the disk may cause them to fall into the planet. The simulations showed that young Jupiter generated a strong planetary magnetic field that created a safe “cavity” around the planet where its young large moons were prevented from migrating too close to their host planet. Young Saturn lacked a strong magnetic field, so only one large moon managed to survive.

“Testing planet formation theory is somewhat difficult because we have only our Solar System for reference, but there are multiple satellite systems close to us whose detailed characteristics we can observe,” says Yuri I. Fujii, primary author of the report announcing these findings. Next, the team is interested in expanding their theory to other moons and potential exomoon systems.

(Credit: Yuri I. Fujii/L-INSIGHT [Kyoto University], Shinichiro Kinosh*ta)

27/03/2026

A rare phenomenon has been discovered with the and other telescopes: a galaxy ~10 billion light-years away dimmed by a factor of 1/20 in just 20 years. Likely caused by a rapid drop in gas feeding its central supermassive black hole.
https://subarutelescope.org/en/results/2026/03/24/3688.html

https://subarutelescope.org > Science Results

06/03/2026

Experience the World's Most Powerful Instrument for Galaxy Exploration with Shadow the Scientists!

Join our "Shadow the Scientists" session and watch real-time observations with ʻŌnohiʻula PFS on the Subaru Telescope as astronomers collect spectra from distant galaxies!

Date & Time:
Wednesday March 11, 7:00 p.m. – 9:00 p.m. (HST; Hawai‘i Standard Time)
Thursday, March 12, 5:00 a.m. – 7:00 a.m. (UTC; Coordinated Universal Time)
Thursday, March 12, 2:00 p.m. – 4:00 p.m. (JST; Japan Standard Time)

Language: English

* Advance registration is required to participate in this Zoom session.

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About Shadow the Scientists

Shadow the Scientists (StS) is a program that connects the public to professional scientists in various scientific disciplines, including connections to professional astronomers through observing experiences with world-class telescopes.

This program was launched in 2020 during the COVID pandemic by a researcher at the University of California, Santa Cruz, in collaboration with ‘Ohana Kilo Hoku, a native Hawaiian non-profit organization supporting astronomy and space programs, and other partners. Through the program, researchers invite members of the public to remotely experience observations with the Subaru, Keck, and Gemini North Telescopes near the summit of Maunakea, Hawai‘i, the Lick Observatory in California, and many other telescopes around the world.
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The ʻŌnohiʻula Prime Focus Spectrograph (PFS) is a wide-field, multi-object spectrograph installed on the Subaru Telescope that began full science operations in March 2025. This instrument can observe approximately 2,400 celestial objects at the same time across a wide field of view. It breaks down the light of each object into a rainbow extending well past the range of human vision, i.e., from the visible to near-infrared light. ʻŌnohiʻula PFS is one of the world’s most powerful tools for capturing and analyzing light from numerous distant objects simultaneously, making it an exceptional instrument for exploring and characterizing large numbers of distant galaxies.

Subaru Telescope staff will also present how the ʻŌnohiʻula PFS was developed, demonstrate how the instrument is operated, and share the meaning of its Hawaiian name, ʻŌnohiʻula.

In addition to watching world-class astronomical observations, participants will have the opportunity to listen to short talks by astronomers, scientists, and telescope operators, and to ask questions during the session. Why not join the StS sessions to remotely experience observations with the Subaru Telescope and to meet and talk with astronomers?

17/02/2026

Rule-Breaking," Extremely Fast-Growing Supermassive Black Hole in the Early Universe

An international research team led by scientists at Waseda University and Tohoku University has discovered an extraordinary quasar in the early Universe that hosts one of the fastest-growing supermassive black holes known at this mass scale. Observations with the Subaru Telescope reveal a striking, rule-breaking combination: the quasar is undergoing extremely rapid accretion while simultaneously shining brightly in X-rays and producing strong radio emission from a jet—features that many theoretical models do not expect to coexist. This unexpected juxtaposition of phenomena offers a new perspective on how supermassive black holes grow in the early Universe.

15/01/2026

Do Even Low-mass Dwarf Galaxies Merge? New Clues from the Outer Stars of a Milky Way Satellite

With the SubaruTelescope, astronomers have discovered a new structure surrounding a tiny satellite galaxy of the Milky Way. The structure provides compelling evidence that even extremely low-mass dwarf galaxies may have experienced mergers in their past.

06/01/2026

Topics: A new-year’s message from the Director General, NAOJ

"Everyone, happy new year of the Horse. I would like to say a few words to mark the start of 2026. ..."

Full message:
https://www.nao.ac.jp/en/news/topics/2026/20260106-new-years-message.html

Everyone, happy new year of the Horse. I would like to say a few words to mark the start of 2026.

25/12/2025

As a SubaruTelescope project, we post two new images monthly on the Subaru Gallery page.
Today image is Barred Spiral Galaxy NGC 4274 and Other Galaxies.

The galaxy at the top of the image is NGC 4274, located in the direction of the constellation Coma Berenices. It is a well-proportioned barred spiral galaxy with ring-like spiral arms and prominent, clearly visible dust lanes. Below it, there are three additional galaxies—NGC 4278, NGC 4283, and NGC 4286—from right to left. The contrast between the spiral and elliptical galaxy morphologies is striking.

https://subarutelescope.org/en/gallery/pressrelease/2025/12/24/3637.html