Almost two years ago, astronomers excitingly reported the first preliminary observations of a potential planetoid at a staggering distance – 132 times further from the Sun than Earth is. That’s four times further out than Pluto. Its orbit and distance have now confirmed it's the furthest object observed yet in the Solar System, and it's been given a cute and fitting nickname.
The planetoid (a small celestial body like a minor planet or asteroid that orbits the Sun) is officially known as 2018 AG37 but was immediately nicknamed "Farfarout" because its discovery came just months after the discovery of another extremely distant planetoid 2018 VG18, then nicknamed Farout.
The team estimates that the planetoid is 400 kilometers (250 miles) across, putting it on the lowest possible range for a dwarf planet (like Pluto) if it is ice-rich. The object was first detected in 2018, but it's taken 2 years to finally confirm it using nine observations over this time that showed the planetoid moving and provided clues about its orbit.
"The discovery of Farfarout shows our increasing ability to map the outer Solar System and observe farther and farther towards the fringes of our Solar System," co-discoverer Dr Scott Sheppard from the Carnegie Institution for Science said in a statement. "Even though some of these distant objects are quite large, being dwarf planet in size, they are very faint because of their extreme distances from the Sun. Farfarout is just the tip of the iceberg of Solar System objects in the very distant Solar System."
"A single orbit of Farfarout around the Sun takes a millennium," added co-discoverer Dr David Tholen from the University of Hawai?i Institute for Astronomy. "Because of this long orbital, it moves very slowly across the sky, requiring several years of observations to precisely determine its trajectory."
Its orbit is really quite interesting. Farfarout was first detected far away from the Sun but the team estimates that during its orbit, it can get much closer, crossing the orbit of Neptune. This particular orbit indicates that Farfarout is likely to have had some strong gravitational interaction with the ice giant planet in the distant past.
"Farfarout’s orbital dynamics can help us understand how Neptune formed and evolved, as Farfarout was likely thrown into the outer Solar System by getting too close to Neptune in the distant past," explained Chad Trujillo from Northern Arizona University. "Farfarout will likely strongly interact with Neptune again since their orbits continue to intersect."
Farfarout will be given an official name after its orbit is better determined over the next few years.