The elusive ninth planet, theorized to be hiding in a distant part of the solar system, may not actually be a planet, a new study suggests. Instead, what we assume is a massive object may be evidence of this. gravity It doesn’t work as we thought. But not everyone likes the new theory.

Hypothesis ninth planetFirst proposed in 2016, it is claimed that the unusual orbits of objects that appear to be moving away from the Sun in the Kuiper Belt beyond Neptune can be explained by the existence of an undiscovered ninth planet with a mass up to 10 times that of Earth. Since then, astronomers have been searching for the ninth planet. But despite searching nearly half of the night sky, they had so far come up empty-handed.

In a new study published September 22 in The Astronomical Journal, researchers propose another explanation for the gravitational anomalies observed in the outer solar system: there are no anomalies. Instead, the team shows that the inconsistencies completely disappear when an alternative concept of gravity known as modified Newtonian dynamics (MOND) is applied.

Isaac Newton’s second law states that the gravitational force that attracts an object is inversely proportional to the distance between it and the object pulling it, meaning that the gravitational force becomes weaker as the distance between two objects increases. However, MOND changes this and assumes that after a certain distance, the gravitational force is directly proportional to the distance, meaning that the gravitational force does not decrease as quickly over large distances. This suggests that objects orbiting larger objects at greater distances, such as stars on the outskirts of spiral galaxies such as the Milky Way, will experience a greater gravitational force than predicted by the second law.

So, according to MOND, Kuiper belt objects are actually being pulled to the rest of our galaxy, not to an undiscovered planet.

The researchers were surprised by their findings. The initial goal of their work was to “rule out” MOND as a possible explanation for the ninth planet. But when they applied this to the problem, it seemed to solve the problem perfectly.

“MOND does a really good job of explaining galactic-scale observations,” said study author Harsh Mathur, a theoretical physicist at Case Western Reserve University in Ohio. “But I didn’t expect this to have a noticeable impact on the outer solar system.”

MOND was first proposed in 1983 as an alternative to dark matter, invisible particles of unknown origin that are thought to make up 27% of all matter in the universe, according to NASA. Dark matter was proposed to explain the “masslessness problem,” which arose when astronomers realized that stars and planets alone could not explain the observed gravitational pull of galaxies. But MOND suggests that if distant objects are subjected to greater gravitational influence, then perhaps there won’t be as much mass loss as we first thought.

However, MOND cannot explain all of the missing mass of the universe and therefore cannot completely rule out the idea of ​​dark matter. Other studies have shown that reconciling MOND with quantum mechanics and relativity requires adding “weird” things to existing theories, and that some of these additions are problematic. Source