The object – provisionally called 2012 VP113 but nicknamed Biden after the US Vice President – is the most distant object in orbit around the Sun, never coming closer than 12 billion kilometres, and sometimes going as far away as 67bn km.
The orbit of Pluto, another dwarf planet that was once thought to be the farthest from the Sun, stretches to 7.4bn km.
The planetoid is thought to be around 450km in diameter and is probably composed of ice and rock. Its colour likely comes from the effects of radiation on frozen water, methane and carbon dioxide that make up its surface. It takes some 4,000 years to complete one orbit.
Scott Shepherd of the Carnegie Institution for Science and Chadwick Trujillo of Gemini Observatory in Hawaii, jointly discovered the planetoid with the Cerro Tololo Inter-American Observatory in Chile in 2012.
“It goes to show that there’s something we don’t know about our solar system, and it’s something important,” Trujillo told Nature, which reported their discovery. “We’re starting to get a taste of what’s out beyond what we consider the edge.”
They think it is from the inner Oort Cloud, a hypothetical region that stretches to the edges of the solar system, up to one light year from the Sun, and is thought to be the source for long-period comets.
Sedna, another dwarf planet discovered (by a team including Trujillo) in 2003 whose orbit overlaps Biden’s, is the only other object known to orbit beyond the Kuiper belt, a sort of super asteroid belt beyond Neptune that includes Pluto.
“They’re in no man’s land,” Sheppard said. “People wondered if Sedna was unique, and 10 years on, we have at last found another object that shows it is not. There is probably a large population of objects out there,” Sheppard said.
Stephen Lowry, a senior lecturer in astronomy and astrophysics at the University of Kent said: “The orbital properties of these two objects are so very different from that of the Kuiper Belt objects that it wouldn’t be wrong to suggest they may be part of the inner Oort Cloud.”
“What is exciting about this work,” said Meg Schwamb, a post-doctoral fellow at the Institute of Astronomy and Astrophysics at Academica Sindica in Taiwan, “is that we know the inner Oort cloud is there. This is the second object we know of, and it’s a smoking gun.”
It is possible that both Sedna and Biden formed closer to the Sun and were later ejected by gravitational forces.
The discovery also adds evidence to the controversial hypothesis that a large planet could be hidden in the distant depths of solar system since Sedna and Biden have orbital similarities.
“If you took a Super Earth and put it a few hundred astronomical units [1 AU = 150m km] out, the gravity could shepherd Sedna and this new object into the orbits they have,” said Sheppard.
Tyche or Planet X, as it is sometimes called, was proposed by Professors John Matese and Daniel Whitmire from the University of Louisiana at Lafayette to explain why 20 per cent of long-period comets arive at a higher angle than predicted by conventional theory. They thought it could be up to four times the size of Jupiter.
However, Nasa’s Wise (Wide-field Infrared Survey Explorer) space telescope reported earlier this month that it could find no evidence for a planet larger than Saturn within 1,500bn km of the Sun.