New Evidence Strengthens Case for Hidden Planet X in Solar System
For over a decade, astronomers have suspected the existence of Planet X, a massive object lurking in the outer Solar System.
A new Princeton University study strengthens this idea, offering compelling evidence based on the orbits of trans-Neptunian objects (TNOs), also called Kuiper Belt objects (KBOs).
“An asymmetry in the orbits of these distant objects would be a reason to think a planet is potentially there,” says Amir Siraj, lead author of the study accepted by The Astrophysical Journal.
Previous studies focused on the most distant KBOs, assuming closer ones were too affected by Neptune’s gravity to show Planet X’s influence. However, Siraj’s team modeled orbits of KBOs that remain stable over billions of years.
Expanding the dataset from 11 to 51 KBOs allowed a stronger statistical analysis, revealing only a one-in-a-thousand chance their alignment is random. “That’s not necessarily a home run,” he says, “but it’s definitely suggestive of a planet being there”.
The team also ran 300 simulations to refine Planet X’s potential properties. They estimate it’s about 4.4 times Earth’s mass, possibly a super-Earth or mini-Neptune, with an elliptical orbit closer to the Solar System than previously thought.
This creates a “treasure-hunt map” for astronomers. Still, its dimness and vast orbital path make pinpointing it challenging.
Mike Brown, a Caltech planetary astronomer and long-time Planet X advocate, welcomes the findings. He believes the Vera C. Rubin Observatory, set to become fully operational within a year, will be crucial.
Its massive camera will scan the entire visible sky every few days, tracking anything that moves.
“I am pretty confident that within the first 18 months, we will have either found [it], or will have made the evidence so irrefutable that no other possibilities exist,” Brown says.
