Astrophysicists Unleash Planetary Power To Probe the Universe’s Deepest Mysteries

Astronomical Telescope in the Earth’s Magnetosphere As Gravitational Wave Detector

The groundbreaking concept proposed by HKUST Department of Physics Prof. Liu’s team allows a single astronomical telescope in the Earth’s magnetosphere to function as a detector for GW signals. Credit: HKUST

Researchers have introduced an innovative gravitational wave detection method using astronomical telescopes to convert gravitational waves into electromagnetic signals within planetary magnetospheres, facilitating the study of the universe’s early stages and cosmic phenomena.

Scientists have proposed a groundbreaking method of detecting high-frequency gravitational waves (HFGWs).  Led by Prof. Tao Liu, Associate Professor from the Department of Physics at the Hong Kong University of Science and Technology (HKUST), the research team’s innovative approach may enable the successful detection of HFGWs by utilizing existing and technologically feasible astronomical telescopes in a planetary magnetosphere. This would open up new possibilities for studying the early universe and violent cosmic events in an effective and technically viable way.

Challenges in Gravitational Wave Observation

Gravitational waves (GWs) are produced by various astronomical phenomena, such as phase transitions in the early universe and collisions of primordial black holes. However, their effects are extremely weak and have been discovered only in relatively low frequency band using the method of interferometry. Observing the universe using GWs thus presents significant technological challenges, particularly in probing the high-frequency band above one kilohertz, where the usage of interferometry becomes strongly restricted.

Breakthrough in Electromagnetic Conversion of GWs

To address this difficulty, Prof. Tao Liu and his postdoctoral fellow Dr. Chen Zhang have collaborated with Prof. Jing Ren from the Institute of High Energy Physics at the Chinese Academy of Sciences, and achieved a significant breakthrough in their recent study. The research capitalizes on the intriguing physical effect that GWs residing within a magnetic field can be converted to potentially detectable electromagnetic waves. By leveraging the extended paths within planetary magnetosphere, the conversion efficiency is increased, yielding more signals of electromagnetic waves. The detection capability can be further enhanced for telescopes with a wide field of view because of the expansive angular distribution of signal flux within such a planet laboratory.

Advantages of the New Detection Method

This innovative method allows a single astronomical telescope to function as a detector for GW signals. By combining multiple telescopes, a wide coverage of HFGW frequencies, ranging from megahertz to 1028 hertz, can be achieved. This frequency range is equivalent to the electromagnetic spectrum used in astronomical observations and includes a large portion that has never been explored in the detection of GWs before. The study provides an initial assessment of sensitivity for satellite-based detectors in low Earth orbit and ongoing missions within Jupiter’s magnetosphere.

The research was published in Physical Review Letters in March and was subsequently highlighted by Nature Astronomy in an article titled “Planet-sized laboratories offer cosmological insights” in May. This emphasizes the significance of the research in paving the way for future studies into novel GW detection technologies.


“Limits on High-Frequency Gravitational Waves in Planetary Magnetospheres” by Tao Liu, Jing Ren and Chen Zhang, 28 March 2024, Physical Review Letters.
DOI: 10.1103/PhysRevLett.132.131402

“Planet-sized laboratories offer cosmological insights” by Morgan Hollis, 21 May 2024, Nature Astronomy.
DOI: 10.1038/s41550-024-02285-w

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