Researchers discovered the farthest known object in our solar system and named it “Farout” (far-out-there). It is about 120 times farther than Earth is from the Sun (120 AU Notes 1). For comparison, the most distant planet, Neptune is about 30 AU from the Sun. At its most distant, once upon a time the ninth planet, now a dwarf planet, Pluto, can be 49 AU (7.29 billion km, or 4.53 billion miles) from the Sun. Currently, Pluto is at about 34 AU, making Farout more than three-and-a-half times more distant than the Solar System’s most-famous dwarf planet.
Farout was first discovered by a team of astronomers in Hawaii in November 2018. The discovery was made by Carnegie Institution for Science’s Scott S. Sheppard, the University of Hawaii’s David Tholen, and Northern Arizona University’s Chad Trujillo.
Its existence was recently confirmed by researchers in Chile and the official announcement was made on December 17, 2018, by the International Astronomical Union‘s (IAU Notes 2) Minor Planet Center. It has been given the provisional designation 2018 VG18.
It was nicknamed “Farout” (Far-out-there) for obvious reasons. Carnegie’s Scott S. Sheppard says “I said ‘far out’ when I discovered it, and it’s a very far out object”.
Researchers think it is a pink dwarf planet that has a diameter of roughly 500 kilometers (310 miles). For
Farout is currently about 11,160 million miles (around 18 billion kilometers) from the Sun. That’s around 120 AU, which is 120 times the distance between the Sun and Earth. This makes it the first Solar System object observed beyond 100 AU.
The pink color and distance from the Sun likely means it has an abundance of ice.
Astronomers have yet to determine the orbit of the dwarf planet.
2018 VG18 was discovered as part of the team’s continuing search for extremely distant Solar System objects, including the suspected Planet X, which is sometimes also called Planet 9. In October 2018, the same group of researchers announced the discovery of another distant Solar System object, called 2015 TG387 and nicknamed “The Goblin,” because it was first seen near Halloween. The Goblin was discovered at about 80 AU and has an orbit that is consistent with it being influenced by an unseen Super-Earth-sized Planet X on the Solar System’s very distant fringes.
Carnegie’s Sheppard says: “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. 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.”
“All that we currently know about 2018 VG18 is its extreme distance from the Sun, its approximate diameter, and its color,” adds University of Hawaii’s David Tholen. “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 discovery images of 2018 VG18 were taken at the Japanese Subaru 8-meter telescope located atop Mauna Kea in Hawaii on November 10, 2018.
Once 2018 VG18 was found, it needed to be re-observed to confirm its very distant nature. (It takes multiple nights of observing to accurately determine an object’s distance.) 2018 VG18 was seen for the second time in early December at the Magellan telescope at Carnegie’s Las Campanas Observatory in Chile. These recovery observations were performed by the team with the addition of graduate student Will Oldroyd of Northern Arizona University. Over the next week, they monitored 2018 VG18 with the Magellan telescope to secure its path across the sky and obtain its basic physical properties such as brightness and color.
The Magellan observations confirmed that 2018 VG18 is around 120 AU, making it the first Solar System object observed beyond 100 AU. Its brightness suggests that it is about 500 km in diameter, likely making it spherical in shape and a dwarf planet. It has a pinkish hue, a color generally associated with ice-rich objects.
- An Astronomical Unit (AU) is the average distance between Earth and the Sun, which is about 93 million miles or 150 million kilometers. Astronomical units are usually used to measure distances within our Solar System.
- The International Astronomical Union is an international association of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy. Among other activities, it acts as the internationally recognized authority for assigning designations and names to celestial bodies (stars, planets, asteroids, etc.) and any surface features on them.