The outskirts of the Solar System is becoming weirder and increasingly fascinating. Astronomers have just discovered a small planetoid that orbits in the most peculiar way around the Sun.
The Trans-Neptunian Object is called Niku, a Chinese word that means "rebellious". And it deserves the name. Niku’s orbit has an 110° inclination, meaning that not only is it almost vertical but also that Niku moves in the opposite direction to all the other major objects in the Solar System.
Niku is 160,000 times fainter than Neptune and is estimated to be less than 200 kilometers (124 miles) in diameter. It’s the second object on such a retrograde orbit, after 2008 KV42. These two discoveries might indicate a population of objects in orbits perpendicular to the Solar System’s plane.
“It suggests that there’s more going on in the outer solar system than we’re fully aware of,” co-author Matthew Holman at the Harvard-Smithsonian Center for Astrophysics, told New Scientist.
The discovery, by the international team of researchers, was possible thanks to the Panoramic Survey Telescope and Rapid Response System 1 Survey (Pan-STARRS 1) on Haleakala, Maui. The study has yet to be peer-reviewed and it can be read on the online repository ArXiv.
According to the astronomers, the data also suggests there might be another orbital plane in the Solar System. It would extend between the orbit of Saturn to three times the orbit of Neptune, and it would require an orbital tilt higher than 60°. Some of the Centaurs, a class of minor planets in the outer Solar System, could be part of this new plane.
At this time, it’s not clear how Niku – or any other object – has achieved such a curious orbit, which keeps it at an average distance of 5.3 billion kilometers (3.3 billion miles) from the Sun. The team even investigated if the mysterious Planet Nine could have played a role, but it seems Niku is beyond its influence.
New surveys like the Large Synoptic Survey Telescope could help discover more objects and hopefully find how Niku and its siblings got where they are.
[H/T: New Scientist]