A gravitational wave detector on the Moon?
An international team of scientists and engineers - including Christophe Collette, researcher at the Aerospace and Mechanical Engineering research unit (School of engineering) and director of the Precision Mechatronics Laboratory at ULiège - is proposing a revolutionary concept to detect gravitational waves on the Moon. The conclusions of this study are published in the Astrophysical Journal.
roduced by the collision of celestial elements, such as black holes or neutron stars, gravitational waves allow us to detect and understand events in our Universe, in a way that is complementary to observations by optical telescopes. Monitoring the vibrational eigenmodes of an elastic body excited by gravitational waves was one of the first concepts proposed for the detection of gravitational waves. The idea of using the Moon itself as part of the detector by exploiting its response to gravitational waves was first pursued by Joseph Weber in the early 1970s. A surface gravimeter was deployed on the Moon in 1972 during the Apollo 17 mission to observe lunar vibrations caused by gravitational waves. However, a design error in the instrument made it impossible to carry out the planned experiment. We now know that even a working gravimeter would not have been sensitive enough to see the astrophysical signals," explains Joris van Heijningen, researcher at UCLouvain. So a new generation of lunar seismometers had to be developed. »
With this in mind, an international team of scientists, led by the Gran Sasso Science Institute (GSSI), is now proposing a new detector concept. Building something as complex as a gravitational wave detector on the Moon is an extremely difficult undertaking," explains Jan Harms, professor at the Gran Sasso Science Institute and INFN associate researcher who is coordinating the Lunar Gravitational Wave Antenna (LGWA) collaboration. So we have to be ingenious.
With new technologies and by taking advantage of the favourable environmental conditions at the Moon's south pole, the published study reveals that a rich scientific field in astrophysics could be opened up. "We would be able to see signals from compact binaries composed of galactic white dwarfs to massive black holes at high redshift," says Roberto Della Ceca, director of the INAF Astronomical Observatory in Brera, "with the potential for revolutionary discoveries. "
At the same time, the seismic sensors of the lunar gravity wave antenna would observe lunar seismic events with unprecedented accuracy. The seismic platform developed as part of the SILENT project that I am leading at the University of Liège is an excellent emulator of the lunar environment, which will make it possible to test and validate the ultra-precise seismometers needed for the LGWA," says Prof. Christophe Collette, Director of the Precision Mechatronics Laboratory at ULiège. Marco Olivieri, a seismologist at the INGV in Bologna, believes that "the data from the LGWA would be of great value to lunar science, as it would shed light on the Moon's internal structure, the mechanisms of moonquakes and the history of the Moon's formation.
The project is now entering a phase of detailed science technology studies and deployment. "We submitted the concept in response to recent calls from ESA and NASA as an idea for a future lunar science mission, and we intend to turn this exciting concept into reality," concludes Jans Harms. "There are undoubtedly some challenges that need to be overcome, but the renewed interest in the Moon from leading spacefaring nations and Europe's exceptional expertise in space technology and exploration will be to our advantage. »
The LGWA team is composed of scientists from several institutions such as : GSSI - Gran Sasso Science Institute, INFN - Laboratori Nazionali del Gran Sasso, INAF - Istituto Nazionale di Astrofisica, INGV - Istituto Nazionale di Geofisica e Vulcanologia, University of Florence, La Sapienza University of Rome, NASA's Goddard Space Flight Center, University of Minnesota, Space Boy Station srl, DARK, Institut Niels Bohr, CNR - Istituto Struttura della Materia and Elettra-Sincrotrone Trieste, RICMASS - Rome International Center for Materials Science - Superstripes, , Observatorio Polifunzionale del Chianti, Université de Liège, département BEAMS, Université Libre de Bruxelles, Université Catholique de Louvain, International Research School of Planetary Sciences, Università d'Annunzio di Pescara, Université d'Amsterdam, Université du Maryland, Université de Genova, Université de Bologne.
HARMS J. & al., Lunar Gravitational-wave Antenna, The Astrophysical Journal, 22 mars 2021