How the dance of death stars puts a new spin on the way suns are born
Chinese astronomers have used this cosmic dance to look into the Milky Way's past and find that stars born today spin much faster than those formed billions of years ago.
Using data from Europe's Gaia space telescope and other sky surveys, researchers at the Changchun Observatory in northeastern China studied thousands of stars, each with a mass roughly 1½ times that of the sun.
They found that as the Milky Way evolved, newly formed stars began spinning up to 10 times faster than their much older counterparts. That extra spin causes gas clouds to break into smaller fragments, making it harder for massive stars to take shape.
The study, accepted for publication in The Astrophysical Journal, presents the first direct evidence that the galaxy's star-forming clouds have grown more turbulent over time.
'Our study shows that the angular momentum of stars in a certain mass range holds key clues to the Milky Way's history,' the team said in a statement on the observatory's website. 'It offers a new way to study how the galaxy has changed over time.'
This shift in the star-forming environment could also reshape our galaxy, gradually favouring the birth of smaller, long-lived stars, while massive stars – and the explosive supernovae they trigger – could become rarer.
Scientists have long relied on a star's chemical make-up, age, and motion to see back into the Milky Way's past.
Stars are born spinning, and how fast they spin depends on the conditions in the clouds that formed them.
Many stars slow down as they age. For instance, when the sun formed about 4.6 billion years ago, it likely took less than 10 days to complete a rotation.
Today, it rotates once every 25 days at the equator. By the time it runs out of fuel and expands into a red giant, it will turn thousands of times more slowly and possibly take centuries to complete one spin.
In the new study, the researchers from Changchun focused on stars between 1.4 and 1.8 times the sun's mass. Unlike the sun, these heavier stars hold on to much of their original spin for billions of years.
Near the end of their lives, these stars expand dramatically. As their size increases, their spin slows.
'It's much like a ballerina extending her arms to slow down as she spins,' the team said, dubbing this final slowdown the star's 'retirement solo'.
By using precise measurements from the Gaia mission, the team compared the angular momentum of thousands of such stars of various ages and found a striking pattern: younger stars spin much faster than older ones – not because the older stars slow down, but because they were born that way.
The finding suggests that the Milky Way's star-forming environment has steadily grown more turbulent and energetic over the past 6 billion years, spinning up new stars with each generation.
The team hopes future studies will refine models of how young stars develop just before they ignite.
They also call for more data on stars with a wider range of chemical compositions, which could help reveal how different types of stars gain or lose spin during formation. - SOUTH CHINA MORNING POST
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
New Straits Times
16 hours ago
- New Straits Times
Chinese soccer team train for inaugural World Humanoid Robot Games
BEIJING: On a soccer pitch in Beijing, "T1" is practising shots and taking up positions. T1 is no ordinary player, however, but a gold medal-winning humanoid robot training for the first World Humanoid Robot Games, taking place in Beijing from August 15. T1 is part of a race to take the lead in humanoid robotics, as China looks to become more self-sufficient in advanced technologies. The Games will bring together teams from more than 20 countries for events ranging from track and field to dance and martial arts, as well as practical applications such as industrial handling and medical services. T1 and its two teammates, fielded by Tsinghua University's Hephaestus team, made history for China last month by winning gold in the "Humanoid, adult size" category of the 28-year-old RoboCup Humanoid League in Brazil. "The Chinese government is actively promoting humanoid robot development," said Zhao Mingguo, Chief Scientist at Booster Robotics, maker of the T1. "To advance technology, the government is actively organising competitive events, and this sports games is one such experience." While some may dismiss such events as gimmicks, industry experts and participants see them as a decisive spur to advance humanoid robots toward practical real-world deployment. Although the Hephaestus team would hardly trouble even junior human opposition, Booster Robotics views soccer as a powerful test of perception, decision-making and control technologies that could later be applied in factories or homes. "Playing football is a testing and training ground for ... helping us refine our capabilities," Zhao said. And just as in real life, moving on from the training ground is often a challenge. Hephaestus is building on software developed for Brazil to improve the players' positioning skills. But the performance of humanoid robots still depends to a great extent on environmental variables such as the surface and hardness of the ground and the gradient of any slopes, according to Hephaestus's Chen Penghui. It wouldn't be the first time a soccer team had visited a new venue and bemoaned the state of the pitch. — REUTERS
The Star
16 hours ago
- The Star
HK universities see success in drive to attract more top talent from abroad
HONG KONG: Professor Gao Yang, a prominent scholar in the fields of robotics and aerospace, left King's College London to join the Hong Kong University of Science and Technology (HKUST) in May after being approached to take up new roles there. While her move back to Asia was primarily driven by her family's needs, she said Hong Kong's current focus on developing its scientific fields at a world-class level as a strategic driver for long-term growth was a major pull factor for her. At the same time, the geopolitical and economic climates elsewhere in the world – in particular, Western countries – have become increasingly challenging for academics to navigate. Said Prof Gao: 'Compared with the greater uncertainties in the UK and Europe, the situation in Hong Kong in terms of the volume and scale of support poured into research, innovation and commercialisation looks a lot more positive, stable and sustainable. The investment in (my field of) aerospace programming definitely seems more determined and committed.' The mainland China-born academic, who has spent 20 years teaching in the United Kingdom after a decade of studying in Singapore, now heads HKUST's Centre for AI Robotics in Space Sustainability as well as its Space Science and Technology Institute, and teaches at its department of mechanical and aerospace engineering. Professor Gao Yang said she was drawn by Hong Kong's current focus on developing its scientific fields at a world-class level. Prof Gao is one of the successes that Hong Kong is seeing in its drive to attract more international talent to teach at the city's top universities. It comes as the Asian financial hub ramps up efforts to develop its artificial intelligence and science, technology, engineering and mathematics (Stem) industries as engines to power future growth in the city. The city has also been increasingly aligning its economic development with China's objectives, which include ramping up technological innovation and scientific research in competition with the United States. Statistics from some Hong Kong universities have shown a notable rise in new faculty appointments from abroad. But that many of these scholars are of mainland Chinese origin has raised some concerns about talent diversity. HKUST, one of the city's eight publicly funded universities, said it had 'welcomed more than 100 top scholars and scientists from mainland China, the United States, Germany, France, South Korea, Singapore and other countries' since it started a global recruitment campaign in October 2022. It 'aims to hire another 100 faculty members', the university told The Straits Times. The Chinese University of Hong Kong (CUHK), also publicly funded, told ST it had 'recruited over 150 leading international and promising young scholars from 15 regions including mainland China, Taiwan, Singapore, South Korea, Australia, New Zealand, Europe and North America' since 2023. Its programmes have been 'attracting top non-local research talents to Hong Kong to participate in innovation and technology development', it added. Hong Kong's education chief Christine Choi also revealed in April that 'world-renowned professors from US institutions are relocating to Hong Kong', driven by tighter visa policies and geopolitical tensions affecting traditional Western study destinations. She declined, however, to provide more details, citing a 'need for discretion to ensure smooth transitions'. Among prominent international scholars who have relocated to Hong Kong over the past year are meteorologist Chen Fei, who worked at the US National Centre for Atmospheric Research for 26 years, and Harvard University-trained economist Jin Keyu, who was a tenured professor at the London School of Economics for 15 years. Both academics joined HKUST. HKUST has been among the most proactive of the city's tertiary institutions in taking advantage of global developments to attract international talent, academics and students alike, to Hong Kong. In May, it promised unconditional offers to Harvard University students immediately after the US government moved to halt foreign enrolment at the college. In Britain, the flagging economy has affected research funding for many academics, as grants are based on a proportion of the country's gross domestic product, noted Prof Gao. 'As this situation carries on, it is likely to affect more domains and bring more academics to Asia,' she told ST. Of her experience in Hong Kong so far, Prof Gao said she was 'completely surprised and amazed by the proactive engagement from sectors including the decision-making think-tanks, businesses, the government and industry to build dialogue' in her field. 'Such seamless collaboration between the scientific community and think-tanks will help make a more profound impact on society beyond just academia,' she added. Over at CUHK, global Stem scholar and prominent mathematics professor Wei Juncheng moved back to Hong Kong in late 2024 after 11 years of teaching at the University of British Columbia (UBC) in Canada. Professor Wei Juncheng said tensions between the US and China have spilt over into Canada, affecting academia as well. Prior to his stint at UBC, Wuhan-born Professor Wei, 57, had taught for 18 years at CUHK after obtaining his doctorate from the University of Minnesota in the US. 'In the last few years, tensions between the US and China have somehow also spilled over into Canada, affecting the environment in academia as well,' Prof Wei told ST. 'Applying for research grants has become more difficult and political for some academics (in Canada),' he said, adding that many mainland-born scholars applying for funding were now required to fill up more forms delving into their backgrounds and specify that they were not researching in areas of strategic sensitivity or those that would help China. Tighter visa restrictions have also impeded global exchanges as the once-frequent Chinese government-sponsored academic visitors can no longer obtain visas to visit Canadian universities for learning and collaboration, he added. There have also been reports of the Chinese authorities restricting educators from leaving the country or visiting universities overseas. Prof Wei said he has observed a large and growing number of mainland-origin academics leaving the West in recent years. 'Despite having been educated in the US, many of my mainland-born academia friends there have moved back to China, with the influx accelerating especially in 2025,' he said. 'I chose to return to Hong Kong as I'm already familiar with CUHK's environment and I still prefer the internet and academic freedom we enjoy here.' The recent inflow of internationally trained scholars into Hong Kong comes after the city's public universities reported a record number of academic staff departures two years ago. Some 7.6 per cent of staff, or 380 out of about 5,000 in the eight institutes, quit in the 2022/2023 academic year, while 7.4 per cent left the year before. The departures coincided with a mass exodus of both local and foreign talent following the Covid-19 pandemic and the imposition of a national security law in Hong Kong in 2020. Some analysts have raised concerns, however, that those hired to fill the vacancies are tilted heavily towards mainland-born scholars, potentially affecting academic diversity. Mainland-origin academics have outnumbered their local counterparts at nearly all of the eight publicly funded universities since 2023. Some 41 per cent of all of the institutes' academic staff are now from mainland China, according to official data. Student numbers in Hong Kong's universities have also increasingly veered towards mainlanders, accounting for 74 per cent of the city's pool of non-local first-year students in the 2024/2025 academic year. Hong Kong's growing number of mainland-born academics is due to both push and pull factors, according to Associate Professor Alfred Wu from the Lee Kuan Yew School of Public Policy in Singapore. 'The push factor is the increasing difficulty for these scholars to continue operating in the West, while the pull factor is that – with Hong Kong now paying a lot more attention to research that integrates well into the Greater Bay Area's (GBA) development plans – it makes academic collaboration much smoother for these scholars, as they understand mainland Chinese culture much better,' Prof Wu told ST. The GBA refers to the region comprising Hong Kong, Macau and nine cities in mainland China's Guangdong province. But the consequent drop in diversity within academia could hinder the city's ability to innovate, adapt to global changes and maintain its competitiveness as an international hub, Prof Wu suggested. 'People need to think long term – having diversity means that we try to reduce our risks by not putting all our eggs into one basket,' he said. 'Decreasing diversity in Hong Kong universities may not be a problem now, but the situation may be different a decade or two down the road if Hong Kong's focus for growth has to shift away from its alignment with mainland China.' - The Straits Times/ANN
The Star
a day ago
- The Star
Does this stone reveal Qin Shi Huang's quest for immortality? A physicist chips in
High on the Qinghai-Tibet Plateau in southwestern China and northeastern India, archaeologists recently discovered a 2,246-year-old stone inscription that might record one of the most mysterious chapters in Chinese history. The stone reads: in the 26th year of Qin Shi Huang's reign, the emperor commanded the five Grand Master Yi to lead a group of alchemists westward to the Kunlun Mountains in search of the elixir of immortality.
