Farout: astronomers identify most distant known object in solar system

Photograph: Scott S Sheppard/David Tholen

Via theguardian.com

A group of astronomers have identified the most distant object ever observed within our solar system.

Provisionally named 2018 VG18, but nicknamed Farout by its discoverers, the body is 120 astronomical units (AU) from the sun. One AU is equal to the average distance from the Earth to the sun, or just under 150m kilometres. The previous furthest known object was Eris, 96 AU from the sun.

The discovery was made by Scott S Sheppard of the Carnegie Institution for Science in Washington DC, David Tholen of the University of Hawaii and Chad Trujillo of Northern Arizona University. It was announced on Monday by the Minor Planet Center.

The same team were responsible for the discovery this year of a minor planet nicknamed The Goblin, 80 AU away. The Goblin’s orbit suggested that it may be influenced by an as yet undiscovered large planet near the edge of the solar system.

However, the team said they did not yet know enough about Farout to tell whether it was being influenced by the putative Planet X.


“2018 VG18 is much more distant and slower moving than any other observed solar system object, so it will take a few years to fully determine its orbit,” said Sheppard. “But it was found in a similar location in the sky to the other known extreme solar system objects, suggesting it might have the same type of orbit that most of them do.

“The orbital similarities shown by many of the known small, distant solar system bodies was the catalyst for our original assertion that there is a distant, massive planet at several hundred astronomical units shepherding these smaller objects.”

Tholen said: “All that we currently know about 2018 VG18 is its extreme distance from the sun, its approximate diameter and its colour. Because 2018 VG18 is so distant, it orbits very slowly, likely taking more than 1,000 years to take one trip around the sun.”

The team say Farout’s brightness suggests it is about 500km (310 miles) wide, and it is probably spherical. It has a pinkish hue, which they say means it is probably covered in ice.

Trujillo hailed the international nature of the discovery, which involved telescopes in Hawaii and Chile owned and operated by Japan, and researchers based in the US.

“With new wide-field digital cameras on some of the world’s largest telescopes, we are finally exploring our solar system’s fringes far beyond Pluto,” he said.

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