In the outer solar system beyond Neptune, the farthest recognized planet from the sun, astronomers have discovered a new object with weird attributes.
The trans-Neptunian object (TNO) called Niku, which means "rebellious" in Chinese, appears to be a chunk of ice measuring about 124 miles in diameter.
There are other objects of the same size and composition in the Kuiper belt and beyond but what made this TNO strange is that it orbits the sun in a plane that is tilted 110 degrees to the plane of the rest of the celestial objects in the solar system.
It also orbits the sun backwards, opposite the direction of the other planets and objects in the solar system.
Scientists are baffled by these odd behaviors but they have a theory on what's behind the weird spin and tilt. Researchers said that objects that do not orbit within the plane followed by the rest of objects in the solar system or that rotate in the opposite direction were possibly knocked off their course by another object.
"It suggests that there's more going on in the outer solar system than we're fully aware of," said Matthew Holman, from the Harvard-Smithsonian Center for Astrophysics, who is part of the team that discovered the TNO using the Panoramic Survey Telescope and Rapid Response System 1 Survey (Pan-STARRS 1).
Holman's team initially considered Planet Nine to be the mysterious object beyond Neptune that could be influencing Niku's orbit.
Planet Nine is a hypothetical planet in the far outer solar system believed to be about 10 times bigger than Earth. If this body exists, it is likely located around 20 times the distance of Neptune from the sun. Despite the popularity of the idea that this ninth planet exists, no actual planet has yet been discovered.
Even if Planet Nine truly exists, further analysis revealed that Niku is too close to the rest of the solar system to be possibly impacted by a Planet Nine. The team that discovered Niku also found that the object is part of a group of objects that circles the sun backwards along the rebellious 110-degree plane path.
"This result may hint at the existence of a large population of similar origin," the researchers reported in their study, which is available for viewing pre-print on Arxiv.
"The mechanism causing and maintaining this common plane is still unknown. The detection of additional high inclination objects in future surveys, such as PS2 or LSST, will provide additional clues as to the dynamical origin of this population."
