Physicists Have Been Searching for a Fundamental ‘Fifth Force’ for Decades. The Bennu Asteroid May Have Brought Them Closer to Finding It

The Standard Model of particle physics suggests that particles interact with each other under the control of four forces: electromagnetic, gravitational, strong nuclear force, and weak nuclear force. For decades, physicists have debated the possibility of additional forces, as well as the extent to which gravity is a force. Until now, the “fifth force” has been a mystery, but now a group of experts believe they hold the key to its discovery.

It’s in asteroids.

The search for the fifth force. A new study suggests that the fifth force may be responsible for some of the observations made by the OSIRIS-REx mission, which NASA sent to the asteroid Bennu to collect samples that returned to Earth a year ago.

In addition to collecting these samples, the OSIRIS-REx instruments gathered important data about Bennu’s orbit. Possible discrepancies between the spacecraft’s observations and predictions based on theoretical models, such as the Standard Model, could provide clues about this hypothetical interaction.

“Interpreting the data we see from tracking Bennu has the potential to add to our understanding of the theoretical underpinnings of the universe, potentially revamping our understanding of the Standard Model of physics, gravity, and dark matter,” Yu-Dai Tsai, a member of the team responsible for the research, said in a press release.

Anomalies. As the researcher explains, the orbits of objects like Bennu often show anomalies. The team proposes using these anomalies to search for the long-awaited “new physics” that will allow them to surpass the current Standard Model.

It’s in the cracks where the models fail and the experts glimpse options that solve the errors and advance physics. That’s why these possible anomalies are so relevant.

Accurate tracking. The team studied tracking data for the Bennu asteroid before and during the OSIRIS-REx mission. Because it’s a potentially dangerous asteroid for Earth, telescopes worldwide have closely tracked its orbital movements since its discovery in 1999.

This monitoring was even more rigorous during the planning and development of the sample collection mission featuring the asteroid. This extensive monitoring provided the team with precise measurements of Bennu’s orbit.

Based on the data collected, the team narrowed down the limits of action that the hypothetical fifth force could represent. The researchers also considered the possible role of a mediating particle in these interactions, something like a separate graviton or, in this case, an ultra-light boson. You can find the details of the study in the paper published in Communications Physics.

From OSIRIS-REx to OSIRIS-APEX. The team plans to continue its search for the fifth force with a new instrument: the asteroid Apophis. This asteroid, also potentially hazardous to Earth, is the second target of the OSIRIS-REx mission, now transformed into the OSIRIS-APEX mission (for Apophis Explorer).

Apophis will make a close approach to Earth in 2029, passing within 20,000 miles of the planet, less than one-tenth the distance to the Moon. Scientists will use this close approach to study the asteroid in detail, and OSIRIS-APEX will have a front-row seat.

A long search. The search for the fifth force is neither new nor limited to astrophysics. Particle accelerators often play a role in the search, such as Fermilab’s Muon g-2 experiment last year. The lab’s experiments revealed an unexpected behavior in muons that experts couldn’t explain using the theory established by the Standard Model.

The implications of discovering this hypothetical force are almost as mysterious as the force itself. However, researchers point out that it could help unravel some of the mysteries of the cosmos, such as dark matter and energy.

Image | NASA

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