Constraints on fifth forces and ultralight dark matter from OSIRIS-REx target asteroid Bennu

The search for fifth forces and the ultralight bosons that mediate them is a significant endeavor in modern physics, motivated by several extensions of the Standard Model. Anomalies in celestial object trajectories have historically led to groundbreaking discoveries, such as Neptune's inference from Uranus's orbital irregularities and the confirmation of General Relativity through Mercury's precession. Near-Earth asteroids, tracked with increasing precision using astrometric measurements, radar astrometry, stellar occultations, and data from satellites like Gaia, offer promising probes for such investigations. Asteroid tracking is crucial for planetary defense initiatives undertaken by NASA and ESA, generating extensive data suitable for probing fundamental physics beyond the Standard Model. This research leverages the OSIRIS-REx mission's data on asteroid Bennu, a NASA mission designed to study the potentially hazardous asteroid (101955) Bennu. OSIRIS-REx, launched in 2016, arrived at Bennu in December 2018 and conducted detailed observations before collecting a sample in October 2020, returned to Earth in September 2023. The mission's precise tracking data provides an exceptional opportunity to test theories of gravity and search for new physics. Specifically, the study focuses on the possibility of deviations from Newton's inverse square law due to the existence of a 'fifth force' mediated by ultralight particles, which are also potential candidates for dark matter and dark energy, and frequently appear in theories such as string theory. Many beyond-the-Standard-Model (BSM) theories incorporating dark matter and dark energy predict such fifth forces. Previous studies have explored the potential of using asteroid and planetary precessions to constrain fifth forces, and this study builds upon that foundation by conducting a rigorous analysis of Bennu's orbit.

A wide array of methods have been used to search for and constrain hidden fifth forces and ultralight particles. These include laboratory and space-based experiments, as well as cosmological and astrophysical observations. Lunar Laser Ranging (LLR), for example, monitors the Earth-Moon distance with high precision, providing strong bounds on the time variability of Newton's constant and the strong equivalence principle. Proof-of-principle studies have suggested the use of asteroid and planetary precessions to set model-dependent limits on fifth forces. Data from planetary ephemerides (like INPOP) have also been used to constrain fifth-force ranges and the effects of a non-zero graviton mass. This study leverages the high-precision data from the OSIRIS-REx mission, providing a more robust and detailed analysis than previous proof-of-principle studies. It also considers data from the asteroid Apophis, which provides a comparative analysis to assess the effectiveness of different datasets. The study focuses on well-motivated BSM models to demonstrate the power of its constraints, but the findings can be extrapolated to a broader range of models exhibiting Yukawa-type fifth forces.

The study focuses on a hypothetical fifth force impacting the motion of celestial objects. It uses a Yukawa-type potential to model this force, which incorporates a mediator particle's mass, introducing a characteristic range to the force's influence. The equation of motion for a celestial body is modified to include the fifth force, along with Newtonian and General Relativity corrections. This modified equation leads to perihelion precession, which can be detected and quantified from the highly accurate tracking data. The study utilizes the JPL Comet and Asteroid Orbit Determination Package, employing a high-fidelity force model. This model accounts for numerous gravitational effects (from the Sun, planets, Moon, and smaller celestial bodies), relativistic effects, and non-gravitational perturbations such as the Yarkovsky effect, solar radiation pressure, and Poynting-Robertson drag. The model is further refined to include the acceleration caused by the fifth force, impacting the asteroid Bennu's trajectory. The data used comprises ground-based optical and radar astrometry data from 1999 to 2018, additional ground-based radar data from three close encounters, and 36 geocentric pseudo-range points derived from OSIRIS-REx's high-gain antenna tracking data during its proximity operations. A least-squares fit is performed to this comprehensive dataset, allowing the estimation of model parameters, including the strength (α) and range (Λ) of the fifth force. The analysis employs a sophisticated numerical approach to solve the equations of motion, considering the effects of the fifth force perturbatively around the Newtonian solution. The analysis is performed for various fixed values of Λ, allowing the estimation of α and other parameters while assessing their uncertainties. The analysis also includes a comparative study of the asteroid Apophis to examine the impact of data quality and quantity on the constraints obtained.

The analysis yielded strong constraints on the coupling strength (α) of fifth forces as a function of the mediator particle mass (ma) or equivalently the fifth force range (Λ). The study focuses on two specific models: a dark photon (A') and a baryon-coupled scalar (φ). The constraints from the OSIRIS-REx data for Bennu were significantly tighter than those from Apophis data, primarily because of the higher-precision measurements by OSIRIS-REx. The strongest constraints are obtained in the mediator mass range of 10^-18 eV to 10^-16 eV, with the tightest bounds around ma ≈ 10^-17 eV (λ ≈ 0.1 au). This sensitivity is influenced by Bennu's eccentricity and semimajor axis. The study quantifies the relationship between the fifth force range (λ) and its coupling strength (α), finding a dependence described approximately by the relation 10^-13λ/km ≈ 1.02 at 2σ for λ << au. This result is compared with similar findings from other studies, including those using INPOP ephemerides. The study shows that the constraints from the OSIRIS-REx data are more robust than those from previous qualitative analyses that relied on less extensive datasets and more simplified force models. The findings are also compared to constraints from other probes, such as planetary motion, Lunar Laser Ranging (LLR), equivalence principle tests (MICROSCOPE), and black hole superradiance studies. While some other probes yield tighter constraints in specific mass regions, this study presents independent and complementary limits, particularly relevant for the mediator mass range of 10^-18 - 10^-17 eV.

The findings demonstrate that asteroid tracking, especially with high-precision data like that from OSIRIS-REx, offers a powerful method to constrain the parameters of fifth forces and ultralight bosons. The constraints derived in this study are among the tightest currently available in the mediator mass range of 10^-18 - 10^-17 eV. This range is particularly relevant because it overlaps with the mass range for fuzzy dark matter models. Although the study doesn't explicitly assume that the ultralight bosons constitute dark matter, the results are still applicable to such models. The study’s robustness stems from its use of a high-fidelity force model and its consideration of various non-gravitational effects. The detailed analysis method helps ensure the significance of the obtained constraints. The results are compared to existing limits derived from other probes, highlighting both the strengths and limitations of asteroid tracking in the context of searching for new physics. The comparison to results using INPOP ephemerides and other independent studies further validates and supports the study's conclusions.

This research presents robust constraints on fifth forces and ultralight bosons, using high-precision asteroid tracking data from the OSIRIS-REx mission. The strongest constraints are found for mediator masses around (10^-18-10^-17) eV, a range of significant interest for models of dark matter and extensions of the Standard Model. The use of sophisticated force models and comprehensive datasets contributes to the rigor of the study. Future improvements are anticipated with data from the OSIRIS-APEX mission (tracking Apophis) and the inclusion of data from a broader range of asteroids and solar-system objects.

While this study employs a comprehensive force model and high-quality data, some limitations exist. The analysis assumes that the fifth force primarily affects the asteroid Bennu, neglecting potential interactions between other celestial bodies. However, the very stringent upper limits on the fifth force strength suggest that this is a valid approximation. Also, while the study considers two specific models (dark photons and baryon-coupled scalars), the findings can be extrapolated to other models exhibiting Yukawa-type interactions. However, the precise translation between the parameters of this study and other models might depend on the specific model details. Future work should explore the implications of relaxing some of these assumptions and investigating a wider range of BSM models.