An as yet undiscovered planet might be orbiting at the dark fringes of the solar system, according to new research.
Too far out to be easily spotted by telescopes, the potential unseen planet appears to be making its presence felt by disturbing the orbits of so-called Kuiper belt objects, said Rodney Gomes, an astronomer at the National Observatory of Brazil in Rio de Janeiro.
Kuiper belt objects are small icy bodies—including some dwarf planets—that lie beyond the orbit of Neptune.
Once considered the ninth planet in our system, the dwarf planet Pluto, for example, is one of the largest Kuiper belt objects, at about 1,400 miles (2,300 kilometers) wide. Dozens of the other objects are hundreds of miles across, and more are being discovered every year.
(See "Three New 'Plutos'? Possible Dwarf Planets Found.")
What's intriguing, Gomes said, is that, according to his new calculations, about a half dozen Kuiper belt objects—including the remote body known as Sedna—are in strange orbits compared to where they should be, based on existing solar system models. (Related: "Pluto Neighbor Gets Downsized.")
The objects' unexpected orbits have a few possible explanations, said Gomes, who presented his findings Tuesday at a meeting of the American Astronomical Society in Timberline Lodge, Oregon.
"But I think the easiest one is a planetary-mass solar companion"—a planet that orbits very far out from the sun but that's massive enough to be having gravitational effects on Kuiper belt objects.
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