Using Earth as a gravitational wave detector? You heard it right! Researchers from the Institute of High Energy Physics, Chinese Academy of Sciences, and the Hong Kong University of Science and Technology have proposed a novel experimental scheme for high-frequency gravitational wave detection. They suggest that planets in the solar system with magnetic fields, such as Earth and Jupiter, could serve as giant detectors for detecting high-frequency gravitational wave signals. The research findings have been published in Physical Review Letters.
The so-called gravitational waves are actually fluctuations in spacetime caused by the intense motion and change of matter and energy. If we liken spacetime to the surface of water, then gravitational waves can be seen as ripples in spacetime. High-frequency gravitational waves refer to waves with frequencies much higher than kilohertz.
In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) successfully detected gravitational waves, opening a new window for observing the universe. Unlike electromagnetic waves, gravitational waves interact weakly with matter, and their detection may unveil the mysterious veil of dark energy and dark matter, presenting a more complete picture of the universe. "The success of the laser interferometer in detecting gravitational waves has driven the planning and construction of a series of similar projects aimed at detecting gravitational wave signals with frequencies below 10 kilohertz," said Ren Jing, a deputy researcher at the Institute of High Energy Physics of the Chinese Academy of Sciences.
It is worth noting that high-frequency gravitational waves with frequencies higher than 10 kilohertz may also be generated during the early universe or the violent activities of extreme dense celestial bodies. The detection of such gravitational waves could provide crucial clues for exploring new physics beyond the standard model.
"However, due to the short wavelengths of these gravitational waves, laser interferometers find it difficult to capture these 'high-pitched' signals." Ren Jing admitted that one detection method relies on the inverse Gertsenshtein effect, through which high-frequency gravitational waves convert into photons in a magnetic field for detection. Various proposals have considered magnetic fields in different environments, but the detection effectiveness of these schemes is limited by various factors.
This time, researchers proposed for the first time to use the planets of the solar system as laboratories to detect high-frequency gravitational wave signals, using scientific satellites orbiting the planets to detect the signals produced by gravitational waves converted in the planetary magnetosphere. "Considering the range of electromagnetic waves observed in astronomical observations, this scheme can cover a wide range of gravitational wave frequencies. Compared with other detection schemes, this scheme also has advantages such as high magnetic field intensity determination, long effective path for gravitational wave-photon conversion, and wide signal flux angular distribution," explained Liu Tao, an associate professor at the Hong Kong University of Science and Technology and one of the authors of the paper.
The research results show that using existing low-earth orbit satellite data, the planetary magnetosphere system is already able to provide stronger constraints on high-frequency gravitational waves over a wide frequency range, covering large portions of gravitational wave frequency bands that were previously unexplored.
Liu Tao stated that this research achievement lays the foundation for innovative gravitational wave detection methods and opens up new perspectives for exploring the hidden corners of the universe.
