3 years ago

# Solar system expansion and strong equivalence principle as seen by the NASA MESSENGER mission

David E. Smith, Maria T. Zuber, Erwan Mazarico, Antonio Genova, Sander Goossens, Gregory A. Neumann, Frank G. Lemoine
The NASA MESSENGER mission explored the innermost planet of the solar system and obtained a rich data set of range measurements for the determination of Mercury’s ephemeris. Here we use these precise data collected over 7 years to estimate parameters related to general relativity and the evolution of the Sun. These results confirm the validity of the strong equivalence principle with a significantly refined uncertainty of the Nordtvedt parameter η = (−6.6 ± 7.2) × 10−5. By assuming a metric theory of gravitation, we retrieved the post-Newtonian parameter β = 1 + (−1.6 ± 1.8) × 10−5 and the Sun’s gravitational oblateness, $J 2 ⊙$ = (2.246 ± 0.022) × 10−7. Finally, we obtain an estimate of the time variation of the Sun gravitational parameter, $G M ⊙ ° ∕G M ⊙$ = (−6.13 ± 1.47) × 10−14, which is consistent with the expected solar mass loss due to the solar wind and interior processes. This measurement allows us to constrain $G ° ∕G$ to be <4 × 10−14 per year.

Publisher URL: https://www.nature.com/articles/s41467-017-02558-1

DOI: 10.1038/s41467-017-02558-1

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