Planet Nine is attributed for the strange looping orbits of some of the space rocks at the outer edge of the solar system, the trans-Neptunian objects (TNOs).
Known as detached objects, these bodies are not affected by the gravity of Neptune or any other known planet in the solar system, and appear disconnected from the rest of the solar system as they orbit the sun. The idea is that gravity of the yet-to-be seen Planet Nine could be influencing the orbits of these bodies.
A new study presented at the American Astronomical Society in Denver, Colorado, however, offers an alternative explanation for the dynamics of detached objects. It points at gravity of smaller space debris instead.
Researchers calculated the orbits of icy objects at the edge of the solar system. They compared these orbits of these objects to the hands of a clock.
Some of these orbits, such as those that belong to asteroids, move like the minute hand while the orbits of bigger objects move slowly like the hour hand. Eventually, however, these hands meet.
The researchers said that the accumulation of these small scale interactions over many years may be responsible for knocking the objects into their strange orbits. As a result, Sedna's orbit goes from normal to detached due to small-scale interactions.
"You see a pileup of the orbits of smaller objects to one side of the sun," said study researcher Jacob Fleisig, an undergraduate student at the University of Colorado at Boulder.
"These orbits crash into the bigger body, and what happens is those interactions will change its orbit from an oval shape to a more circular shape."
New Theory Did Not Prove Planet Nine Does Not Exist
The new theory, however, has its lapses. For one, it failed to account for other phenomena attributed to Planet Nine.
A 2016 study published in the Astronomical Journal suggested that the strange tilt of the sun in the solar system is caused by an undiscovered planet 10 times the size of the Earth. Fleisig admitted that the computer model they used failed to provide an explanation for the tilting of the sun's axis relative to the inner planets.
Konstantin Batygin, from California Institute of Technology and Planet Nine supporter, said that the model also requires a significant amount of mass in the Kuiper Belt's smaller objects.
"[The] detachment of Sedna-type orbits can be explained by any sufficiently strong external gravitational potential, independent of where it comes from," he said. "For this model to work, you must assume a large, hidden reservoir of undetectable mass in the distant Solar System."