Astronomers have spotted the farthest known object in our solar system — and they've nicknamed the pink cosmic body "Farout."

The International Astronomical Union's Minor Planet Center announced the discovery Monday.

"Farout" is about 120 astronomical units away, which is 120 times the distance between Earth and the sun, or 18 billion kilometres. The previous record-holder was the dwarf planet Eris at 96 astronomical units. Pluto, by comparison, is 34 astronomical units away.

The Carnegie Institution's Scott Sheppard says the object is so far away and moving so slowly it will take a few years to determine its orbit. At that distance, it could take more than 1,000 years to orbit the sun.

Solar system distances to scale showing the newly discovered 2018 VG18 'Farout' compared to other known solar system objects. (Roberto Molar Candanosa/Scott S. Sheppard/Carnegie Institution for Science)

Sheppard and his team spied the dwarf planet in November using a telescope in Hawaii. Their finding was confirmed by a telescope in Chile.

"I actually uttered 'farout' when I first found this object, because I immediately noticed from its slow movement that it must be far out there," Sheppard wrote in an email. "It is the slowest moving object I have ever seen and is really out there."

It is an estimated 500 kilometres across and believed to be round. Its pink shade indicates an ice-rich object. Little else is known.

The discovery came about as the astronomers were searching for the hypothetical Planet X, a massive planet believed by some to be orbiting the sun well beyond the orbit of Pluto.