Photo 1: A high resolution image of the Moon with the simulation of the four LGWA seismometers. Credits: Joris van Heijningen (UCLouvain)
Photo 2
: Assumed location of the LGWA lander on the lunar surface
LGWA the new project to measure gravitational waves from the Moon.
A lunar antenna to measure vibrations of the cosmos and study lunar geology
is the idea of the team coordinated by GSSI
Is it possible to detect gravitational waves even on the Moon? This is the challenge proposed by the international team of scientists and engineers led by Jan Harms, professor at the Gran Sasso Science Institute and INFN research associate, who coordinates the collaboration for the construction of a lunar gravitational-wave antenna, the Lunar Gravitational-Wave Antenna (LGWA).
“We have submitted our project to the attention of ESA – European Space Agency and NASA North American Space Agency as one of the objectives of a future lunar mission which could thus offer this exciting idea the possibility of becoming a reality – explains Jan Harms.
The proposal, presented in the study published in the Astrophysical Journal, is to make the Moon itself part of a gravitational detector by exploiting its intrinsic response to gravitational waves.
This idea was the basis of Joseph Weber's work in the early 70s and led to the creation of the Lunar Surface Gravimeter, a gravimeter placed on the lunar surface in 1972 with the Apollo 17 mission. The objective was in fact to observe the lunar vibrations caused by gravitational waves, but a design error in the gauge made it impossible to perform the experiment.
“Building something as complex as a gravitational wave detector on the Moon is an extremely challenging undertaking. The collaboration and involvement of different subjects and expertise is needed,” says Jan Harms who leads the team of more than 80 scientists in Italy, Belgium, Holland, the United States, Denmark and then Switzerland and the United Kingdom.
The technologies used for the construction of a lunar antenna for gravitational waves, placed at the south pole of the satellite in optimal environmental conditions, could open up new scenarios for astrophysics.
"There is great potential for future revolutionary discoveries - comments Roberto Della Ceca, director of the INAF Astronomical Observatory in Brera - We would be able to see signals from compact binary systems consisting of galactic white dwarfs up to huge black holes at cosmic distances" .
“Today we know that a gravimeter like the one devised by Weber, even if it worked, would not have been sensitive enough to see astrophysical signals. We need to develop a new generation of lunar seismometers,” explains Joris van Heijningen of UCLouvain, part of the team working in Belgium on a new concept of a “lunar seismometer”.
Seismic sensors from the LGWA project could record lunar seismic events with unprecedented accuracy. "The data from LGWA would be of great value for lunar science, shedding light on the internal structure of our satellite, on the mechanisms of moonquakes, i.e. lunar earthquakes, and on the history of the formation of the Moon", explains Marco Olivieri, seismologist of the INGV Section of Bologna.
The project is now entering a phase of detailed analysis and evaluation of the scientific technologies employed and their development.
“Of course, some challenges still need to be overcome. But there is a constant and renewed interest in the Moon by many nations and space agencies. The exceptional experience acquired in Europe and above all in Italy for technologies and explorations in space play in our favor”, concludes Jan Harms.
The team that published the LGWA study is currently composed of experts from
GSSI - Gran Sasso Science Institute, INFN - Gran Sasso National Laboratories, INAF - National Institute of Astrophysics, INGV - National Institute of Geophysics and Volcanology, University of Florence, Sapienza University of Rome, Space Boy Station srl, CIRA - Center Italian Aerospace Research, Chianti Multipurpose Observatory, D'Annunzio University of Pescara, University of Padua, University of Bologna in collaboration with other American and European research groups.
Currently, the search for gravitational waves is entrusted to three interferometers, the VIRGO gravitational wave observatory (operating in Italy at the European Gravitational Observatory, EGO), the LIGOs (two twin detectors in Louisiana and in the state of Washington in the USA ) which will be joined by the Japanese KAGRA (in Kamioka, in the prefecture of Gifu). For the future, the choice of the site where to build the Einstein Telescope, a pioneering third-generation observatory that Italy has applied to host, is under discussion . In space, the European Space Agency's (ESA) LISA Pathfinder mission, completed in 2017, successfully tested the concept of detecting gravitational waves from space, paving the way for the construction of the LISA (Laser Interferometer Space Antenna), whose launch into orbit is expected around the mid-30s.
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