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Exclusive: ‘Like ripples on the sea’: Chinese astronomer tells Global Times how the Milky Way got its newly discovered ‘wrinkles’_我的网站
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Chinese astronomers have discovered that the Milky Way is not a simple, smoothly warped disk, but contains widespread "wrinkle-like" structures resembling ripples on a water surface, providing new clues to understanding the galaxy's 3D structure and evolutionary history.
The discovery was made by a research team from the Purple Mountain Observatory (PMO) under the Chinese Academy of Sciences, using data from the "Milky Way Imaging Scroll Painting" (MWISP) survey. The findings were published online titled "Widespread corrugations superimposed on the Galactic warp in the outer CO disk" in the journal Nature Astronomy on August 7.
For decades, astronomers have known that the Milky Way's disk is not perfectly flat. Instead, its outer regions are slightly bent upward on one side and downward on the other - a structure known as a galactic warp.
However, the latest study shows that this large-scale bending is not the whole story. Smaller-scale vertical fluctuations are also embedded within the warped disk, creating a more complicated 3D structure.
"In many illustrations and in the public imagination, the Milky Way looks like a flat vinyl record," Sun Yan, associate researcher at PMO and the first author of the paper, told the Global Times on Tuesday. "In reality, the outer part of the Milky Way is more like a record that has been heated and deformed, with one side lifted and the other side lowered. That is the warp. On top of this large-scale deformation, there are additional smaller waves, which we call corrugations," Sun explained.
Using a more everyday analogy, Sun compared the Milky Way's structure to a sea surface. The warp is like a large swell that changes the overall height of the ocean, while corrugations are smaller waves superimposed on that swell.
"The two structures exist together. In our data analysis, we first removed the large-scale warp model, which allowed us to reveal the smaller wave-like patterns hidden underneath," Sun said.
The research focused on the Milky Way's outer gas disk rather than the more familiar stellar disk. According to Sun, cold molecular gas and stars provide two complementary ways to study the galaxy.
"Molecular gas is a sensitive probe for studying the vertical structure and dynamics of the galactic disk because it is concentrated near the disk plane and responds strongly to disturbances," she said.
Molecular gas is also the raw material for star formation, meaning its distribution is closely connected with the formation of young stars. The researchers traced this gas through carbon monoxide (CO) emission, which can penetrate regions obscured by interstellar dust and provide a different perspective from optical observations of stars.
The breakthrough was made possible by the MWISP survey, conducted using China's 13.7-meter millimeter-wave telescope.
"MWISP can be understood as giving the Milky Way a large-scale medical examination using millimeter-wave observations," Sun said.
Previous CO surveys were limited in sensitivity and coverage, making it difficult to accurately study the distant outer regions of the galaxy. In contrast, the latest study identified more than 30,000 molecular cloud samples, covering about half of the Milky Way's outer disk and extending to a distance of about 26 kiloparsecs from the Galactic center.
With such a large dataset, researchers were able to first establish a model of the overall warp and then separate subtle structures from the background. The newly identified corrugations have radial wavelengths of about 3.9-7.9 kiloparsecs and vertical amplitudes of about 100-200 parsecs.
The study also identified a corrugation structure extending about 40 kiloparsecs in azimuth at a distance of around 12.7 kiloparsecs from the Galactic center. In some spiral arm regions, vertical displacements can reach approximately 200 parsecs.
The researchers believe these large-scale vertical fluctuations are likely related to "bending waves" triggered by external gravitational disturbances, suggesting that the Milky Way might have experienced more complex interactions during its evolutionary history.
Although the newly discovered structures sound dramatic, they do not have any direct impact on Earth or the solar system. "Humans cannot directly sense these corrugations," Sun said. "Their scales reach thousands or even tens of thousands of light-years, and even if these structures are evolving, such changes would not be directly perceptible on human timescales."
The study focuses on the outer disk of the Milky Way and does not include the region around the solar system. "There is currently no evidence that these structures have any observable influence on Earth's environment," Sun said.
Instead, their significance lies in what they reveal about the past. Like geological layers recording Earth's history, these galactic structures preserve traces of the Milky Way's evolutionary journey, the researchers explained.
Researchers said future studies combining more precise motion measurements and numerical simulations could further reveal the origins of these structures and their role in the long-term evolution of the Milky Way.
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On Monday afternoon, American teacher Ronald Sakolsky visited the homeland of Chinese desert fighter Yin Yuzhen in Uxin Banner of Ordos, Inner Mongolia Autonomous Region. This was a place the American man had visited in 2000 and it has completely changed since then.
In 1999, Sakolsky, a teacher in a China-US education exchange program, was touched by a report on Yin and her husband's afforestation efforts in the harsh wilderness of Mu Us Desert, and raised $5,000 to support her green cause. During that visit, they took pictures - in front of the sunken pit where the Yin couple once resided and in the barren land with a finger-thin sapling they had just planted against a backdrop of dust and bare earth.
What has the $5,000 changed?
On Monday, they came to the Sakolsky forest - a permanent tribute honoring Sakolsky's early contribution to the region's ecological revival - and replicated the vintage pictures, standing in front of a pit that has long been abandoned and beside a newly planted sapling. This time, however, there are bushes and trees in the background.
This contrast not only witnessed their friendship across time and the Pacific Ocean, but also showcased a promise Yin has kept for 27 years and a green dream that has been made possible through generations of joint unwavering efforts from Yin, her husband and countless other sand fighters.
Homecoming with family cooking
Yin hosted Sakolsky on Monday at her home, filling the air with the aroma of home-cooked meals during their long-awaited reunion. Watermelons were served along with other fresh fruits and vegetables, all harvested locally. Yin told the Global Times earlier that she learned the English word "more" to persuade him to eat more.
In 1999, Yin had few options for showing her hospitality, so she cooked a bowl of plain noodles for Sakolsky. Now, the harsh wasteland has transformed into a vibrant green oasis, thanks to unwavering afforestation efforts.
In the courtyard, the Global Times reporter saw Yin grinning from ear to ear with pride as she introduced the produce from the farmland - green pepper longer than a palm, a bottle gourd even bigger than Yin's head, and bags of foxtail millet packaged with the assistance of Yin's grandchildren, who are proud of the family's generations of commitment to green causes.
During a tour of Yin's home, Sakolsky was impressed by the beautiful house with its green courtyard, saying "You deserve every centimeter of this house." Throughout the visit, he repeatedly praised Yin's hands, which the desert fighter and model worker used to change both the land and her own life through arduous work.
The $5,000 Sakolsky donated in 1999 was equivalent to three years' income for Yin's entire family at the time. Today, that money has grown into more than 50,000 trees.
But Yin's journey did not stop there. Over the following decades, with the support of China's growing ecological restoration policies — including subsidies for afforestation and compensation for forest managers — she transformed the barren land into a productive family forest farm. Her success has inspired many others in the region to take up tree planting and sand control, transforming what was once a desperate struggle into a sustainable livelihood.
From the sandy hollow where the Yin couple lived in in 1985 and the earth hut they resided in until 1993, to the solid brick house Sakolsky saw when he last visited, and the two-story house the big family now lives in, the change in living environment is a clear example of ecological dividends.
Uxin Banner lies in the heartland of the Mu Us Desert. The desertification rate was over 90 percent in the 1950s and forestation coverage was merely 7.2 percent as of 1980. Now, the forestation rate has increased to 33 percent, while plantation coverage has expanded to 85 percent, per official data.
Carry on the greenness, kindness
This miracle would have been impossible without numerous people like Yin, long-term systematic planning and scientific governance.
Chen Ziliang, an expert from the local forestry and grassland bureau, said that Mu Us Desert's sand‑control journey has evolved from collective afforestation to contract desert‑reclamation, moving beyond the simple goal of "keeping trees alive" to restoring vegetation based on water‑resource conditions.
Putting the idea of "lucid waters and lush mountains are invaluable assets" into practice, Uxin Banner no longer views "greenness" and "growth" as an either‑or proposition. On restored sandy lands, the under‑forest economy, eco‑agriculture and eco‑tourism have flourished. Sand‑fixing shrubs are now processed into animal feed and biomass fuel, and local authorities are exploring photovoltaic‑powered desert control, the Global Times learned.
Sand control is no longer just about keeping sand away; it's a development approach that guarantees a greener and better living environment alongside a booming economy and increasing incomes.
On Monday afternoon, when Sakolsky finally stepped into the forest named after him, this American teacher witnessed the Chinese woman's perseverance and commitment to her promises. The $5,000 donated without expectations has grown into a thriving forest of around 50,000 trees.
"A promise is a promise. Ms. Yin fulfilled her promise," Sakolsky said. After 27 years, the wasteland is green, and Sakolsky and Yin are "brother and sister."
"This is the answer to how we guide young people: We must teach them love and perseverance. We need to show young people photos of Ms. Yin planting trees, digging the soil with her bare hands," Sakolsky remarked while packing a jar of sand. He said he planned to bring it back to the US, telling his grandchildren it is not just a jar of sand, but "a jar of love."
Sakolsky told the Global Times earlier that the younger generation only knows about the dust-covered landscape from photos and stories of the elderly. It is important to tell them how the greenness is achieved, and how every single person can contribute to making an extensive forest in the harshest environment.
"I see where China and America can work together. I see it, so I will not quit. She [Yin] never quit. 'Quit' is not in her vocabulary," Sakolsky said with emotion on Monday.
"Chinese and Americans can be family. We can get over the differences if we focus on the similarities... If we focus on our similarities and not our differences, we can solve the problems."
At the end of Monday's schedule, Yin and Sakolsky planted another sapling together, just as they did about three decades ago, but in a completely different landscape.
This new sapling carries on the story of not only greenness through generations of joint efforts, but also kindness across the Pacific Ocean.
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