This illustration imagines what the distant object nicknamed “Farfarout” might look like in the outer reaches of our Solar System. Credit: NOIRLab/NSF/AURA/J. da Silva
With the help of the international Gemini Observatory, a Program of NSF’s NOIRLab, and other ground-based telescopes, astronomers have confirmed that a faint object discovered in 2018 and nicknamed “Farfarout” is indeed the most distant object yet found in our Solar System. The object has just received its designation from the International Astronomical Union.
Farfarout was first spotted in January 2018 by the Subaru Telescope, located on Maunakea in Hawai‘i. Its discoverers could tell it was very far away, but they weren’t sure exactly how far. They needed more observations.
“At that time we did not know the object’s orbit as we only had the Subaru discovery observations over 24 hours, but it takes years of observations to get an object’s orbit around the Sun,” explained co-discoverer Scott Sheppard of the Carnegie Institution for Science. “All we knew was that the object appeared to be very distant at the time of discovery.”
Sheppard and his colleagues, David Tholen of the University of Hawai‘i and Chad Trujillo of Northern Arizona University, spent the next few years tracking the object with the Gemini North telescope (also on Maunakea in Hawai‘i) and the Carnegie Institution for Science’s Magellan Telescopes in Chile to determine its orbit.  They have now confirmed that Farfarout currently lies 132 astronomical units (au) from the Sun, which is 132 times farther from the Sun than Earth is. (For comparison, Pluto is 39 au from the Sun, on average.)
Farfarout is even more remote than the previous Solar System distance record-holder, which was discovered by the same team and nicknamed “Farout.” Provisionally designated 2018 VG18, Farout is 124 au from the Sun.
However, the orbit of Farfarout is quite elongated, taking it 175 au from the Sun at its farthest point and around 27 au at its closest, which is inside the orbit of Neptune. Because its orbit crosses Neptune’s, Farfarout could provide insights into the history of the outer Solar System.