NSF’s NOIRLab looks at a body that the Gemini Observatory spotted in 2018 and that astronomers working at Hawaii’s Subaru telescope nicknamed Farfarout. Now, they’ve confirmed that the dim rock really is the most distant object in our solar system:
“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.
“Farfarout was likely thrown into the outer Solar System by getting too close to Neptune in the distant past,” said Trujillo. “Farfarout will likely interact with Neptune again in the future since their orbits still intersect.”
Farfarout is very faint. Based on its brightness and distance from the Sun, the team estimates it to be about 400 kilometers (250 miles) across, putting it at the low end of possibly being designated a dwarf planet by the International Astronomical Union (IAU).