A potential “fifth force” — an unknown force beyond the known four fundamental forces — might influence the paths of celestial bodies. However, recent research on asteroid Bennu shows no evidence of any such force affecting its orbit, setting a limit on how strong this mysterious force could be. This finding, published in Communications Physics on 20 September, provides fresh perspectives on how forces might interact with dark matter, a major unsolved question in physics.

Bennu’s Orbit Examined with NASA’s OSIRIS-REx Mission

NASA’s OSIRIS-REx mission monitored Bennu’s trajectory with extraordinary precision. It played a crucial role in allowing scientists to detect the slightest of deviations in the asteroid’s path. The spacecraft also collected a sample from Bennu that returned to Earth in 2023. According to Dr. Yu-Dai Tsai, physicist at Los Alamos National Laboratory, Bennu’s trajectory data has been analysed meticulously, giving scientists a unique opportunity to look for subtle shifts in its orbit that could hint at forces beyond our current understanding.

Investigating Forces and Particles in the Universe

The study of forces in physics often involves identifying particles associated with them. For instance, photons, particles of light, are responsible for electromagnetic interactions. Should a fifth force exist, its particle might be responsible for dark matter, an enigmatic component of the cosmos. Using Bennu’s orbital data, scientists explored this possibility, narrowing down the potential characteristics of such particles to extremely light masses, approximately a millionth of a trillionth of an electron’s mass.

Expanding the Search Across the Solar System

With these findings, researchers suggest that analysing the orbits of additional asteroids could further test for any signs of the fifth force, potentially revealing a larger range of particle masses. While the physical samples from Bennu offer insights into its material composition, its precise trajectory could eventually deepen our understanding of forces and particles connected to dark matter.