Category: 7. Science

Until now, thin and thick disks have only been identified in the Milky Way and nearby galaxies. It has been impossible with previous telescopes to distinguish the thin edge of a distant galaxy when viewed from the side.

That changed with the launching of the James Webb Space Telescope (JWST) in 2021, which is currently the largest telescope in space.

An international team of researchers has examined 111 JWST images of distant edge-on galaxies, ones where the alignments enabled the researchers to observe the galaxies’ vertical disk structures.

Takafumi Tsukui (formerly of the Australian National University and now based at Tohoku University), who led the research team, says that observing distant galaxies is like using a time machine, allowing us to see how galaxies have built their disks over cosmic history.

“Thanks to the JWST’s sharp vision, we were able to identify thin and thick disks in galaxies beyond our local universe, some going as far back as 10 billion years ago.”

The study revealed a consistent trend: in the earlier universe, more galaxies appear to have had a single thick disk, while in later epochs, more galaxies showed a two-layered structure with an additional thin disk component. This suggests that galaxies first formed a thick disk, followed by the formation of a thin disk within it. In more massive galaxies, this thin disk appears to have formed earlier.

The study estimated the thin disk formation time for Milky Way-sized galaxies to be around 8 billion years ago. This figure aligns with formation timelines for the Milky Way itself, where stellar ages can be measured.

To understand the revealed sequential formation from thick to thin disks and the corresponding formation timelines, the team not only examined the stellar structure but also the motion of gas, direct ingredients of stars obtained from the Atacama Large Millimeter/submillimeter Array (ALMA) and ground-based surveys in the literature. These observations supported a coherent formation scenario:

• In the early universe, galactic disks are rich in gas and highly turbulent
• Intense star formation in the turbulent disks gives rise to thick stellar disks
• As stellar disks develop, they help stabilize the gas disks and reduce the turbulence
• As the disk calms, a thin stellar disk forms inside the pre-developed thick stellar disks
• Whereas larger galaxies can efficiently convert gas into stars, forming thin disks earlier

Tsukui emphasizes that the images provided by JWST help answer one of the biggest questions in astronomy: was our galaxy’s formation typical or unique? “The JWST images provided a window into galaxies that resemble the Milky Way’s early state, bringing us valuable insights from galaxies far away.”

The team hopes that their study will help bridge studies of nearby galaxies with far away ones and refine our understanding of disk formation. The study was published in the journal Monthly Notices of the Royal Astronomical Society on June 26, 2025.

Planets form in disks composed of low-temperature molecular gas and dust, known as protoplanetary disks, found around protostars. Protostars are stars still in the process of forming. The nascent planets are too small to observe directly, but the gravity from a planet can create detectable patterns like rings or spirals in a protoplanetary disk. However, it is difficult to know when these patterns first appeared due to the limited number of protoplanetary disks that are close enough to Earth to be observed in high resolution.

A research team led by Ayumu Shoshi of Kyushu University and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) used improved data processing techniques to search for previously overlooked signs of planet formation in archive data from the ALMA (Atacama Large Millimeter/submillimeter Array) radio telescope. The team reanalyzed data for 78 disks in the Ophiuchus star-forming region, located 460 light-years away in the direction of the constellation Ophiuchus. More than half of the images produced in this study achieved a resolution over three times better than that of previous images.

The new high-resolution images show ring or spiral patterns in 27 of the disks. Of these, 15 were identified for the first time in this study. Combining this new sample with pervious work for a different star-forming region, the team found that the characteristic disk substructures emerge in disks larger than 30 au (astronomical units, 1 au = 149,597,870,700 m, the distance between the Earth and the Sun) around stars in the early stage of star formation, just a few hundred thousand years after a star was born. This suggests that planets begin to form at a much earlier stage than previously believed, when the disk still possesses abundant gas and dust. In other words, planets grow together with their very young host stars.

Once upon a time, the tale of Chang’e flying to the moon existed only in Chinese folklore. But today, that ancient myth has been given a new, modern twist with actual moon samples making their way not to the palace of the moon goddess, but to the headquarters of the United Nations in Vienna.

On June 25, during the 68th session of the UN Committee on the Peaceful Uses of Outer Space, China organized an exhibition featuring lunar samples collected from both the near and far sides of the moon to celebrate 20 years of its lunar exploration program. The exhibition not only showcases China’s remarkable technical achievements, but also offers a window into the country’s vision of inclusive, peaceful and cooperative outer space exploration.

The lunar samples, collected by the Chang’e-5 and Chang’e-6 missions respectively, represent landmarks in space science. Chang’e-5’s successful mission in 2020 made China the third country to retrieve materials from the moon after the United States and the Soviet Union. Chang’e-6 went even further, bringing back the first samples from the moon’s far side in 2024, marking another remarkable achievement for China.

But China’s space program is not just about national pride or technical triumphs. The underlying message of the exhibition is a clear one: China’s space exploration is open to the world.

The journey of Chang’e lunar exploration projects is no longer a solitary leap but a shared path. Over the past two decades, whether through bilateral agreements, joint missions, data-sharing or talent exchanges, China has made cooperation an important part of its space ambitions. The Chang’e-6 mission, for example, carried scientific payloads from France, Italy, Pakistan and the European Space Agency.

China has agreed to share samples with other countries, because they belong not only to China, but also to the world, representing a shared treasure for all humanity. This approach reflects China’s principle of enhancing international cooperation in space on the basis of equality and mutual benefit, peaceful utilization and inclusive development. In a world where geopolitical tensions sometimes spill into the space domain, China’s emphasis on multilateralism and peaceful cooperation sends a timely and constructive signal.

China’s space exploration achievements extend far beyond lunar missions. It made history with its Tianwen-1 mission to Mars, launched in July 2020 as China’s inaugural independent interplanetary endeavor. This groundbreaking mission, for the first time ever, successfully deployed an orbiter, lander and rover on the Red Planet in a single launch.

China also operates two cutting-edge solar observation satellites in orbit. These sophisticated spacecraft have delivered significant breakthroughs, providing scientists with unprecedented insights into the behavior and characteristics of the sun.

In fact, China has gone a step further by proposing the establishment of an open and inclusive platform for deep-space exploration, inviting countries, developed and developing alike, to participate in upcoming missions. For example, China has signed cooperation agreements with 17 countries and international organizations on the International Lunar Research Station construction, offering various levels and forms of collaboration opportunities. The first batch of experimental projects selected through China’s collaboration with the United Nations Office for Outer Space Affairs are being conducted aboard the Chinese space station.

And just like the legend of Chang’e, what once felt distant and mythical is becoming part of a shared human story.