Searching for a Fifth Force of Nature Using Asteroids

The research paper is “Asteroid astrometry as a fifth-force and ultralight dark sector probe”. Here is the abstract.

We study for the first time the possibility of probing long-range fifth forces utilizing asteroid astrometric data, via the fifth force-induced orbital precession. We examine nine Near-Earth Object (NEO) asteroids whose orbital trajectories are accurately determined via optical and radar astrometry. Focusing on a Yukawa-type potential mediated by a new gauge field (dark photon) or a baryon-coupled scalar, we estimate the sensitivity reach for the fifth-force coupling strength and mediator mass in the mass range m≃10^{-21}10^{-15} eV. Our estimated sensitivity is comparable to leading limits from torsion balance experiments, potentially exceeding these in a specific mass range. The fifth forced-induced precession increases with the orbital semi-major axis in the small m limit, motivating the study of objects further away from the Sun. We discuss future exciting prospects for extending our study to more than a million asteroids (including NEOs, main-belt asteroids, Hildas, and Jupiter Trojans), as well as trans-Neptunian objects and exoplanets.


Here’s wishing the investigators Good Luck. I tried to read their paper, but the only part I understood was the statement:

However, such studies are not without challenges, as asteroid trajectories are subject to several perturbations, ranging from gravitational effects from other celestial objects, to non-gravitational effects due to the thermal and reflective properties of the asteroid’s surface.”

Sounds challenging, when the uncertainties may be larger than the effect being pursued. Still, it is an intriguing approach to look out to the universe to try to understand postulated fundamental forces stemming from the sub-atomic level.

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In the interview, he says that one of the main advantages of using asteroids as probes of motion in the solar system is that the ones that occasionally come close to the Earth allow radar ranging which permits determining their instantaneous position and velocity to within 40 metres, much more precise than any body other than the Moon (where Apollo and Luna missions left retroreflectors that allow laser ranging with centimetre precision). But the Moon’s orbit is so fantastically complicated due to perturbations from the Earth (and its lumpy gravitational field), Sun, and other planets that it wouldn’t be useful looking for these tiny effects. Asteroids are small enough to be treated as point sources for location, but massive and dense enough they are much less affected by light pressure, the solar wind, and differential thermal effects compared to a spacecraft.

What would be ideal, he says, is if a future sample return mission to a near Earth asteroid were to leave a package on the surface with a radio transponder and atomic clock. This would dramatically increase the precision in tracking its orbit and make smaller new physics effects detectable.

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