Mysterious ‘unseen planetary mass’ lurking at edge of solar system
Scientists at the University of Arizona's Lunar and Planetary Laboratory (LPL) put forward evidence that this unknown “planetary mass object” may explain why the plane of the solar system is warped in the outer reaches of the Kuiper Belt.
The Kuiper Belt lies beyond the orbit of Neptune and hosts a vast number of minor planets, mostly small, icy bodies and a few dwarf planets.
All planets in our solar system orbit around the sun on the same plane but, according to the measurements made by the research team, the most distant Kuiper Belt objects (KBOs) appear to be tilted away from this by about eight degrees.
This indicates that something unknown is warping the average orbital plane of the outer solar system.
“The most likely explanation for our results is that there is some unseen mass,” says Kat Volk, lead author of the study. “According to our calculations, something as massive as Mars would be needed to cause the warp that we measured.”
The tilt angles of the orbital planes of more than 600 objects in the Kuiper Belt were analyzed for the study.
“We expect each of the KBOs’ orbital tilt angle to be at a different orientation, but on average, they will be pointing perpendicular to the plane determined by the sun and the big planets,” Volk said.
As the team observed KBOs further out, they found that the average plane actually warps away from the invariable plane.
They noted that the chance of the warp being a statistical fluke was no more than 2 percent.
The paper also ruled out the possibility that the mysterious object could be ‘Planet 9’, pointing out that this planet is predicted to be much bigger and much farther out. Planet 9’s existence is unconfirmed, but is expected to be located at more than 200 times Earth's distance from the sun.
“That is too far away to influence these KBOs,” Volk said.
The data does not rule out the possibility that the warp could result from more than one planetary mass object.
Details of the study conducted will be published in the Astronomical Journal.