Test of the equivalence principle for galaxy’s dark matter by lunar laser ranging

authored by
Mingyue Zhang, Jürgen Müller, Liliane Biskupek

Having 50 years of unique observations, lunar laser ranging (LLR) is used to test central elements of Einstein’s theory of relativity, like a possible temporal variation of the gravitational constant or metric parameters. Here, we focused on a possible violation of the equivalence principle (EP) due to assumed dark matter in the galactic center. According to the EP, Earth and Moon experience the same acceleration in the gravitational field of any matter including the galactic dark matter. In the latter case, a violation of the EP would cause an Earth–Moon range oscillation with a sidereal-month period. Recent LLR measurements with high accuracy give us the opportunity to carry out high-precision EP tests for dark matter. We estimated the amplitude of a possible sidereal range oscillation from LLR post-fit residuals. First, we analyzed the characteristics of the residuals for each station and selected a subset of best LLR data. Using this dataset, we obtained 0.6 ± 1.0 mm (realistic error) as a final result for the sidereal amplitude in the direction of the galactic center. It strongly limits a possible violation of the EP for galaxy’s dark matter. Our investigations also show that, for the EP test, a good orbit coverage with good data is more relevant than the number of data or a long time span. As verification, a spectral analysis of the non-uniform LLR residuals has been performed. There again, no significant sidereal signal was found, confirming our previous result.

Institute of Geodesy
External Organisation(s)
Institute of Geodesy and Geophysics, Chinese Academy of Sciences (IGGCAS)
University of the Chinese Academy of Sciences (UCAS)
Celestial Mechanics and Dynamical Astronomy
Publication date
Publication status
Peer reviewed
ASJC Scopus subject areas
Modelling and Simulation, Mathematical Physics, Astronomy and Astrophysics, Space and Planetary Science, Computational Mathematics, Applied Mathematics
Electronic version(s)
https://doi.org/10.1007/s10569-020-09964-6 (Access: Closed)