What astronomers believed to be the most distant object in the Solar System, “Farout,” has lost its title after just two years. That crown now goes to “Farfarout” (zero points for creativity, you guys), a planetoid that is more than 130 times farther from the Sun than Earth is.
As spotted by Inverse, after years of observations, astronomers have confirmed that the planetoid designated by the Minor Planet Centre as 2018 AG37, nicknamed Farfarout, is the farthest known Solar System object at 132 astronomical units away from the Sun.
A single AU is the average distance from the Earth to the Sun, aka about 148 million kilometres. (For reference, the previous titleholder Farout, officially designated 2018 VG18, is “just” 120 AU away.) That means Farfarout is roughly 19.7 billion kilometres away, or for context, about four times farther away from the Sun than Pluto. At that distance, the planetoid completes a single orbit around the Sun just once in a millennium.
“Because of this long orbital period, it moves very slowly across the sky, requiring several years of observations to precisely determine its trajectory,” said David Tholen, an astronomer at the University of Hawaii’s Institute of Astronomy and member of the team behind the discovery, said in a statement this week.
The same team — Tholen, the Carnegie Institution for Science’s Scott Sheppard, and Northern Arizona University’s Chad Trujillo — originally spotted the planetoid in 2018 using the Subaru 8-metre telescope located atop the dormant volcano Mauna Kea in Hawaii. In the years since, they’ve used the Gemini North telescope, also located on Mauna Kea, and the Magellan telescope in Chile to determine Farfarout’s orbit and confirm its status as the farthest known object in our Solar System.
“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,” said Sheppard in this week’s statement. “Only with the advancements in the last few years of large digital cameras on very large telescopes has it been possible to efficiently discover very distant objects like Farfarout.”
There’s still much that scientists don’t know about this incredibly distant planetoid, but they’ve uncovered a few clues in their research. The team believes it’s at the “low end” of the dwarf planet scale “assuming it is an ice-rich object,” and has an estimated diameter of roughly 400 km. It has an incredibly elongated orbit that crosses paths with Neptune, leading scientists to speculate that Farfarout may once have been a much closer planetary neighbour, but possibly strayed too close to Neptune and was jettisoned to the outer reaches of our Solar System as a result of the much larger celestial body’s gravity.
Astronomers believe that studying Farfarout may offer insight into how Neptune formed and evolved in our Solar System, and the two are likely to interact once again due to their intersecting orbits.
It’s uncertain how long Farfarout will hold onto its title, especially given the rapid advancements of our Earthly telescopes. Sheppard called the planetoid “just the tip of the iceberg of solar system objects in the very distant solar system.” Who knows, maybe by this time next year we’ll have a FarfarFARout on our hands.