Homegrown cosmic camera to snap the invisible in stardust
13 May 2026
Stars are born beneath a veil of dense interstellar dust known as molecular clouds, beyond the visual reach of conventional human tools such as optical lenses and X-rays.
To pierce this veil, CUHK is leading an interdisciplinary ensemble to develop the first submillimetre polarimetric camera designed by a Chinese research team. One of the aims of the instrument is to cut through the cosmic haze and shed light on the long-standing mystery of how stars come into being.
Hong Kong’s space frontier
“If you asked a student in Hong Kong what they associated with astronomy, they would likely point to NASA, the Hubble Space Telescope or LIGO – things that feel distant and foreign,” says Professor Li Huabai of CUHK’s Department of Physics, referring to the National Aeronautics and Space Administration and its gigantic optical device, and to the Laser Interferometer Gravitational-Wave Observatory, all facilities of the United States.
His ambition is to bridge that perceived divide by spearheading the Remote Observing from Greenland (ROGer) project to develop the camera. The project serves as a precedent for developing advanced astronomical instruments in Hong Kong, which he hopes will inspire young people to see the field as an attainable career path in Hong Kong.
The endeavour begins by addressing a perennial challenge: the difficulty of capturing submillimetre signals.
Submillimetre radiation, hovering between infrared and microwave wavelengths, is emitted by some of the coldest objects in the universe – such as molecular clouds, the dense structures in which stars are forged. Its study is therefore essential to unravelling the mechanism of star formation.
However, radiation within this band is exceptionally weak. Atmospheric water vapour further absorbs much of it while introducing substantial noise often hundreds of times stronger than the target signal, thereby hampering observation.
To counter such interference, submillimetre telescopes must be sited at high altitudes in arid environments. Yet, even on the Greenland plateau, current technology fails to filter out atmospheric noise entirely. This persistent hurdle has left submillimetre astronomy an underexplored frontier.
Astronomy tool built from the ground up
In 2021, CUHK’s Physics and Statistics and Data Science departments launched the ROGer project jointly with the University of Hong Kong (HKU) and international partners to develop a submillimetre polarimetric camera for deployment in Greenland by 2029. The project name is both an acronym for Remote Observing from Greenland and a tribute to Professor Roger Hildebrand, a pioneer of polarimetric astronomy and mentor to Professor Li.
To date, the project has secured two rounds of funding from the Research Grants Council – an initial HK$3 million, followed by HK$7.96 million under the Collaborative Research Fund. Researchers have finished building a prototype camera and are refining and testing it.
ROGer works like the sensor in a digital camera. It will be installed on a submillimetre telescope in Greenland that serves as its lens, forming a complete astronomical imaging system.
To tackle the stubborn problem of sky noise, the research team has innovated a technique that detects orthogonal polarisation signals. The technique capitalises on the fact that sky noise is largely unpolarised whereas submillimetre signals often carry distinct polarisation directions. It allows ROGer to identify and cancel out non-polarised atmospheric interference, allowing the target signals to stand out and significantly improving observational accuracy.
Further, the researchers have developed a Sky Noise Simulator that recreates a range of observational conditions for laboratory testing. By simulating varying levels and intensities of noise, they can train and assess its ability to eliminate interference.
Seeing the invisible: magnetic fields and the birth of stars
Stars are born when molecular clouds collapse, which is why these dense gaseous structures are often described as stellar nurseries. Yet why only a fraction collapses to form stars remains unresolved. “Many theories suggest that magnetic fields play a decisive role,” says Professor Li’s teammate, postdoctoral physics researcher Dr Lyu Weitao, “but the exact mechanisms are still under debate. We hope to answer it through direct observation.”
Although magnetic fields cannot be observed directly, they can be inferred through submillimetre polarimetric observations. “The human eye can perceive only the brightness and colour of light – its intensity and frequency – but light has another dimension: polarisation,” Dr Lyu explains.
ROGer can detect the direction and degree of submillimetre polarisation, allowing scientists to map the otherwise invisible magnetic fields within molecular clouds. Under magnetic influence, molecular clouds’ dust grains align in a particular way and produce a polarisation signature on the submillimetre radiation they emit. By analysing these signals, researchers can reconstruct the relationship between magnetic fields and other forces, may draw closer to understanding the origins of stars.
Once deployed, ROGer will be made available to other research teams in Hong Kong. For instance, another project co-lead Professor Stephen Ng Chi-yung at HKU has proposed using the instrument to observe neutron stars.
City without vast skies reaching for the stars
Hong Kong may lack ideal conditions for astronomical observation, but Professor Li believes it offers fertile ground for engineering sophisticated astronomical instruments. With its concentration of talent and sustained public investment in frontier research, he thinks the city’s capabilities can rival leading institutions in the world.
For Li, ROGer represents more than a technical milestone; it is a vital educational pursuit. “Witnessing a professional instrument built locally from scratch will make astronomical science feel far less distant to our students and general public,” he says. “It shows that a career in the field need not be pursued only overseas – the journey can begin here.”
| Project leads (front row, from left) | Postdoctoral physics researcher Dr Lyu Weitao |
| Professor Fan Xiaodan of Statistics and Data Science | |
| Professor Li Hua-bai of Physics | |
| Professor Otto Akseli Hannuksela of Physics | |
| Researchers (back row, from left) | Sun Jialin |
| Cao Yujie | |
| Xu Yitao | |
| Catherine Yu Xinrui | |
| Zhuang Zi | |
| Quan Feiyu |
By Jessica Chu
Photos by Steven Yan
