New Print about TRAPPIST-1e: Could People Discover Gravity Theory in a Compact System?

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This study adopts the viewpoint of a hypothetical observer on TRAPPIST-1e and uses N-body integrations to generate ephemerides and observable sky phenomena in the compact TRAPPIST-1 system. It asks which classical and relativistic gravitational signatures would be testable there: Keplerian regularities (retrograde motion, transits, mean-motion correlations, and Great Inequality-like behavior) are directly observable, but relativistic effects are comparatively faint.

The simulations show that retrograde motion episodes are 1-2 orders of magnitude shorter than in the Solar System but occur more frequently, and transits of the inner planets are stably observable. Because orbital eccentricities are low, Kepler’s first law is hard to notice; by contrast, Kepler’s second and third laws can be verified with high precision within ~10^2 days (swept-area variation <= 0.01%, and the constant inferred from a and P is accurate to <= 2%). Mean-motion correlations can also suppress a clear Great Inequality signature.

By comparison, general-relativistic perihelion precession is only ~0.1% of the Newtonian precession signal, far smaller than in Mercury’s case, so GR would likely remain undiscovered for such observers. The overall conclusion is that compact exoplanet systems permit fast, precise tests of classical gravity, but only partial development of gravity theory beyond Newtonian dynamics would be feasible locally.