An international team of astronomers has discovered the furthest object ever detected in the Solar System. Nicknamed “Farout”, it’s a small round object with a pinkish hue located 17.95 billion kilometers (11.15 billion miles) from the Sun. The color is common in ice-rich objects.
Its official designation is 2018 VG18 and it is 500 kilometers (310 miles) in diameter. It's the first object discovered further than 100 astronomical units (AU) from our star, with 1 AU being the Earth-Sun distance. Farout is at a distance of 120 AU, significantly further out than dwarf planet Eris, which is at 96 AU. Pluto, by comparison, is at 34 AU.
The object was discovered in images taken with the Japanese Subaru Telescope atop Mauna Kea in Hawaii on November 10. Follow-up observations to confirm the distance were conducted in December from Las Campanas Observatory in Chile.
“All that we currently know about 2018 VG18 is its extreme distance from the Sun, its approximate diameter, and its color,” co-discoverer David Tholen, from the University of Hawaii, said in a statement. “Because 2018 VG18 is so distant, it orbits very slowly, likely taking more than 1,000 years to take one trip around the Sun.”
Farout adds to the intriguing family of peculiar objects so far discovered beyond the orbit of Pluto. The orbits of these trans-Neptunian objects (TNOs) seem to be influenced by the gravity of a massive planet so researchers have put forward the idea that Planet 9 exists over 200 AU from the Sun. So far the search hasn’t uncovered definitive proof, but TNOs are helping astronomers understand what’s going on at the edge of the Solar System.
“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,” added co-discoverer Scott Sheppard, from the Carnegie Institution for Science. “But it was found in a similar location on 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 AU shepherding these smaller objects.”
While we are only just starting to understand the further rims of the Solar System, discoveries like this show that there are still many worlds out there left to find.