Primordial Black Holes May Alter Earth’s Orbit, Cause Planets and Moons Near Us to Wobble

In a recent study, scientists suggest that some of the oldest black holes in the universe swoop past the Solar System at least once every decade and cause planets and moons to wobble and rock. If scientists detect this event, it would provide the first proof that these cosmic voids exist as dark matter.

What is a Primordial Black Hole?

Black holes are some of the most strange objects in the cosmos, being regions of immense gravity that not even light can escape. The most bizarre among them are primordial black holes (PBH), the hypothetical cosmic voids that are believed to have formed when dense, hot regions of space collapsed in the second right after the Big Bang.

PBHs are projected to have masses ranging from a hundred-thousandths the mass of a paper clip to that of 100,000 suns, depending on when they were born during the one-second interval. Some astronomers believe that primordial black holes with masses between asteroids Eros and Juno are the most important because they could be primarily made of dark matter. This mysterious material holds together the components of galaxies.

There is a problem with this claim, though. No astronomical observation yet has definitively identified black holes of this type and mass. They remain elusive despite asteroid-like mass since their size ranges between a hydrogen molecule and an average bacterium.

New Insights on PBHs

If such a primordial black hole were to encounter Earth, it would not destroy our planet. However, scientists led by Tung X. Tran hypothesized that these PBHs could subtly affect the other objects in the Solar System. Their conclusion is discussed in the paper "Close encounters of the primordial kind: a new observable for primordial black holes as dark matter".

The team's claim suggests that the distances of planets from the Sun or the Earth could change over time. If a primordial black hole flies by a planet, it could make that planet wobble or rock slightly around the path it was taking before the flyby. Measuring these periodic swaying in the distance could, therefore, reveal the passage of a PBH.

The researchers reached this conclusion by calculating how close a primordial black hole would have to whizz past an object in the solar system before its movement is altered. They discovered this distance could be as considerable as a few astronomical units.

The experts also performed simulations to calculate the changes in the trajectories of the planets or moons. These were made using data about the positions of planets and moons taken from the JPL Horizons database. The team assumed that a primordial black hole with the mass of an asteroid could come within two astronomical units of the sun. After several years, the orbits of the planets and moons would wobble by around one or more inches or even several feet.

Detecting these wobbles and confirming that they result from PBH flybys remains extremely challenging. It turns out that astronomers have precise measurements of how far particular celestial objects are from Earth, as provided by numerous space missions such as Martia rovers, which have helped calibrate the distance from Earth to Mars to 4 inches (10 centimeters).

On the other hand, this is not the case with other celestial objects. The error margins of some measurements are very similar to the distances by which a PBH pushes planets. This means that even if the paths of such celestial bodies change, scientists still could not determine if it was because of an instrument error or an actual PBH. Researchers, therefore, need more precise simulations and higher-quality observations.