Trans-Neptunian Object Spotted Defying the Norms Of Our Solar System
Astronomers have no idea what this minor planet is doing at such a weird orbital inclination with respect to the rest of the solar system.
It’s been dubbed Niku after the Chinese word for “rebellious.”
Why? Because this trans-Neptunian object (a faint, minor planet located outside the orbit of Neptune) circles the Sun at an extreme 110° tilt with respect to the plane of our solar system.
It also orbits in retrograde—opposite the direction of most other objects in the solar system, including all eight planets. A team of astronomers including Matthew Holman at the Harvard-Smithsonian Center for Astrophysics
just discovered it .Here’s Shannon Hall, reporting for New Scientist:
To grasp how truly rebellious it is, remember that a flat plane is the signature of a planetary system, as a star-forming gas cloud creates a flat disk of dust and gas around it. “Angular momentum forces everything to have that one spin direction all the same way,” says Bannister. “It’s the same thing with a spinning top, every particle is spinning the same direction.”
That means anything that doesn’t orbit within the plane of the solar system or spins in the opposite direction must have been knocked off course by something else. “It suggests that there’s more going on in the outer solar system than we’re fully aware of,” says Matthew Holman at the Harvard-Smithsonian Center for Astrophysics, part of the team that discovered Niku using the Panoramic Survey Telescope and Rapid Response System 1 Survey (Pan-STARRS 1) on Haleakala, Maui.
Astronomers have a preoccupation with finding the famed Planet Nine, a celestial body that might provide an answer as to why high-incline objects like Niku exist in the first place. They’ve noted the existence of Centaurs, which are similar to trans-Neptunian objects except that they cross the orbits of one or more of the giant planets. (You can learn more about the differences between trans-Neptunian objects—or Kuiper Belt objects—and Centaurs here .)
Various of these objects could feasibly offset the gravitational pull of a larger, yet-to-be-discovered ninth planet . But Holman says Niku doesn’t fit the criteria of these types of objects, which means astronomers have no idea what Niku is doing at such a weird angle.
Image credit: NASA