Researchers in China have successfully tested the optical core of a space-based instrument designed to detect gravitational waves.

The team at the Institute of Mechanics under the Chinese Academy of Sciences (CAS) built and validated a full-function interferometer optical core, a key measurement component for the Taiji observatory project.

Taiji is a space-based gravitational wave project designed to detect massive cosmic waves rippling through the fabric of spacetime. In ground tests, the team confirmed that their new component met the requirements for the Taiji-2 mission.

Detecting gravitational waves over vast distances

Gravitational waves are ripples in spacetime produced by cataclysmic events, such as the collision of supermassive black holes or the explosive death of a star.

Space-based systems like Taiji are capable of detecting lower-frequency gravitational waves from the far reaches of space. Unlike ground-based gravitational wave detectors, they are not limited by seismic noise and interference from Earth.

The Taiji project envisions a triangular formation of three spacecraft separated by millions of kilometers. According to a report from the South China Morning Post (SCMP), they will connect using laser interferometry to measure minute changes in distance caused by passing waves.

The CAS team’s new optical core achieves picometer-level precision. Incredibly, this means it is capable of detecting displacements as small as one ten-thousandth of the diameter of a human hair.

According to the researchers behind the project, it incorporates features that suppress temperature-induced interference, and it has demonstrated a tenfold improvement in measurement stability alongside substantially reduced noise levels.

The three-step Taiji program

The Taiji program follows a three-step roadmap. Taiji-1, which flew to space in August 2019, successfully tested laser interferometry and drag-free control in orbit. Now, the new optical core will form part of the Taiji-2 demonstration mission, which will involve two satellites. Finally, Taiji-3 will see the full three-satellite observatory lifted to space at some point in the 2030s.

“The ground tests [of the optical core] were a success, and all the key numbers met the strict demands of the mission,” the scientists said in their report. “That means that the core measurement system of Taiji has officially moved from [theory] to real hardware.”

In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO), located in the US, became the first to directly detect gravitational waves. Now, Taiji represents China’s entry into space-based gravitational wave astronomy. Other initiatives, such as the European Space Agency’s LISA project, are also aiming to uncover the mysteries of the cosmos with large-scale gravitational wave detectors.

By targeting the millihertz frequency band, Taiji could reveal mergers of intermediate-mass black holes, provide insights into the early universe, and test general relativity on large scales.

The team published their results in a new paper in the international journal Research.