"FarFarOut" officially added to count of dwarf sized planets in distant Solar System

(Photo credit: Roberto Molar Candanosa, Scott S. Sheppard from Carnegie Institution for Science, and Brooks Bays from University of Hawaiʻi.)
Photo credit: Roberto Molar Candanosa, Scott S. Sheppard from Carnegie Institution for Science, and Brooks Bays from University of Hawaiʻi
Wednesday, February 10, 2021 

A team of researchers including Carnegie astronomer Scott Sheppard confirmed the most distant object ever observed in our Solar System. The object is officially named 2018 AG37 but is nicknamed "FarFarOut" for just how far away from the Sun it is orbiting—about 132 AU, where 1 AU is the distance between the Earth and Sun. At that distance, it takes an entire millennium to orbit the Sun.

Sheppard and his colleagues David Tholen (University of Hawaii) and Chad Trujillo (Northern Arizona University) have been surveying the sky since 2012 to map the Solar System beyond Pluto. FarFarOut joins a set of these planetoid discoveries—including the previous record holder, FarOut at 124 AU that was discovered by the same team.  However, the team is still on the hunt for “Planet X”—a much larger planet that could be orbiting somewhere just beyond Farfarout.

Like a giant game of connect the dots, each new discovery fills in a bigger picture of our very distant Solar System and points astronomers closer to what may be hidden at the fringes of our Solar System. However, because Neptune strongly interacts with Farfarout as Farfarout’s orbit crosses Neptune’s orbit, Farfarout motion across the sky cannot be used to determine if there is another unknown massive planet out there.

Only objects that stay in the very distant Solar System, well beyond the gravitational effects of Neptune, can be used to probe the very distant Solar System for the signs of another massive planet. These include objects like Sedna and 2012 VP113 (nicknamed Biden). Although they are currently closer to the Sun at around 80 AU, they never approach Neptune in their orbits around the Sun and thus would be strongly influenced not by Neptune but more by other possible massive objects in the distant solar system, like the possible Planet X.

Said Scott Sheppard in a recent press release, "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.” He continued, "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.  Even though some of these distant objects are quite large, 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."