On October 21, a significant collaboration was announced between the Square Kilometer Array (SKA) and China’s Tianlai Project, which focuses on detecting dark energy through radio observations. This partnership was recently certified by the International SKA Organization, marking a milestone for both initiatives.
The SKA, a revolutionary next-generation radio telescope being constructed through international cooperation, involves member countries such as China, South Africa, the UK, and Australia. As a part of its Pathfinder project, SKA incorporates various large-scale scientific instruments related to its scientific and technological goals. Even though construction is underway, the ongoing research from the Pathfinder projects continues to offer fresh opportunities for scientific discovery and the testing of new detection technologies in the context of the SKA.
Robert Braun, the SKA’s Science Director, emphasized that the Pathfinder initiatives are crucial to paving the way for the SKA’s development. Despite entering an initial operational phase, the existing radio antennas and experimental projects will still provide valuable insights for SKA’s scientific programs.
So, what does the Tianlai Project aim to achieve? Led by the National Astronomical Observatory of China (NAOC) in the Xinjiang region, the Tianlai Project’s goal is to test key technologies for detecting dark energy and to create a three-dimensional map of matter distribution in the universe. The term “Tianlai,” inspired by Zhuangzi’s philosophy, refers to the natural voice of the universe, specifically the baryon acoustic oscillations.
Current astronomical models indicate that approximately 70% of the universe is composed of mysterious dark energy, which contributes to its accelerating expansion. While dark energy itself cannot be observed directly, its characteristics and prevalence can be studied by examining the universe’s expansion over time. The cosmic microwave background generated by the Big Bang has left its mark on the early distribution of matter, which has evolved into the large-scale structures we observe today. By studying these structures, astronomers can analyze the oscillation of baryon acoustic waves and derive the expansion rate of the universe.
The Tianlai Project primarily focuses on detecting the 21-centimeter radio signals emitted by neutral hydrogen atoms—one of the most abundant elements in the universe. As the universe expands, these signals have redshifted to longer wavelengths. Tianlai’s design allows for the observation of 21-centimeter signals and their redshifts across a broad wavelength range, enabling a detailed understanding of the universe’s three-dimensional matter distribution.
The project team includes researchers and graduate students from the NAOC and various Chinese universities, along with experts from institutions in the United States and France. As a vital research platform in China’s field of radio astronomy, the Tianlai Project is also instrumental in cultivating talent within the realm of radio detection technologies.
Looking ahead, Tianlai’s capabilities are set to grow even further. Chief Scientist Chen Xuelei from the NAOC noted that they have established two types of array configurations – a cylindrical array featuring three parabolic reflector antennas with 96 feeds, and a dish array comprising 16 six-meter parabolic antennas. These configurations are designed to test techniques related to neutral hydrogen surveys and data processing methods, all of which can be integrated into the SKA project.
To enhance their observational reach, the Tianlai team is implementing a wide-field design for their radio interferometer array, which aligns with SKA’s broader scientific objectives, including the search for fast radio bursts originating from deep within the universe beyond our galaxy.
“As we conduct real observations and analyze the data, we can uncover practical issues that theoretical analyses alone might overlook,” Chen said. He also mentioned that, with support from Northeastern University, Tianlai has recently expanded by adding three new arrays near the existing ones, improving its detection capabilities for accurately locating fast radio bursts.
