Contrary to what simplified Styrofoam ball models of the solar system from grade school taught us, our planetary neighborhood contains much more than the sun and major planets orbiting it. There are tons of asteroids, ice chunks and minor planets far beyond Neptune also orbiting our favorite star. Researchers have now located the most distant object seen yet: a minor planet they’ve temporarily dubbed “Farout.”
According to Sarah Lewin at Space.com, Farout—whose official name is 2018 VG18—was first spotted in November by researchers using the Subaru 8-meter telescope in Hawaii. Its existence was then confirmed using the Magellan telescope at Las Campanas Observatory in Chile. Those observations show that the object is about 300 miles across and spherical, making it a dwarf planet. Its pinkish color also suggests that it is covered in ice. The celestial body was found about 120 astronomical units (AU) away, or 120 times the distance of the Earth to the sun. For comparison, Pluto orbits at 34 AUs and Eris, the former farthest observed object in the solar system, is 96 AUs away.
“All that we currently know about 2018 VG18 is its extreme distance from the sun, its approximate diameter, and its color,” says David Tholen, a researcher at the University of Hawaii, in a press release. “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 was discovered while researchers searched for the elusive Planet X or Planet 9, a large planet believed to be orbiting the sun at the far edges of the solar system that could explain some of the strange orbits of minor planets and space rocks beyond Pluto. Farout, however, doesn’t fit the bill.
“Planet X needs to be several times larger than Earth in order to gravitationally push the other smaller objects around and shepherd them into similar types of orbits,” co-discoverer Scott S. Sheppard from the Carnegie Institution for Science tells George Dvorsky at Gizmodo. “Planet X is also likely even further away, at a few hundred AU.”
Scientists aren't sure of Farout's exact orbital path yet. It could be that gravity from a nearby large planet like Neptune tugs on it and it will orbit toward the giant planet region of our solar system, says Sheppard. However, if its orbit leads further outward and deeper into space, it could mean Planet X has a hold on it.
While Farout is truly far out, Lewin at Space.com emphasizes that it’s the farthest object we’ve observed. We know that other objects swing even deeper into space, though we haven’t seen them in action. The orbit of the dwarf planet Sedna, for instance, should take it 900 AUs away from the sun. And it’s hypothesized that our solar system is surrounded by a shell of rocky and icy objects between 1000 and 100,000 AUs away called the Oort Cloud. But those objects are so far away, we haven’t been able to catch a glimpse yet, though there are several comets that astronomers believe may have journeyed from that distant edge of our solar system closer to our own cosmic neighborhood.