Astronomers have spotted a distant world that orbits far beyond Pluto, in the extreme reaches of the Solar System.
The object, known informally as L91, may be in the process of gradually shifting its way inward from the Oort cloud — a reservoir of comets and other icy bodies — into the equally icy Kuiper belt. No object has ever been seen doing this.
The discovery of L91 reveals more about the extreme worlds whose orbits lie beyond the gravitational influence of Neptune, the most distant giant planet in the Solar System. Researchers have yet to fully explain how these bodies end up in their current orbits. “Every time we find another one of these objects it adds another piece to the puzzle,” says Meg Schwamb, a planetary scientist at Gemini Observatory in Hilo, Hawaii. Astronomers with the Outer Solar System Origins Surveydiscovered L91 in September 2013 using the Canada-France-Hawaii Telescope in Hawaii. The group has been conducting a detailed survey of a small portion of the sky, aiming to catalog and describe the Kuiper belt objects within. The location and trajectory of L91 make it “fascinating”, said Michele Bannister, an astronomer at Queen’s University Belfast. She reported the finding on 17 October at a joint meeting of the American Astronomical Society’s Division for Planetary Sciences and the European Planetary Science Congress. L91 may have been tossed into its remote orbit by gravitational interactions with Neptune in the distant past. “This one is right on the hairy edge of everything,” says Nathan Kaib, an astronomer at the University of Oklahoma in Norman.