Our first story today is far out. Correction. It’s actually ‘Farfarout’, which is the unofficial name for a solar system object recently discovered by a team using the Subaru 8-meter telescope at Maunakea in Hawai’i. Follow up observations were performed with the Gemini North and Magellan telescopes to determine the orbit of this newly found world, and it is truly far, far out there. In fact, it’s so far, far out there that it now holds the record for the most distant object observed in our solar system, edging out the previous record-holder, Farout.

Astronomers cannot be trusted to name things. And yet, these names amuse us.

So just how far, far out there is this world? It is currently out at 132 AU from the Sun, almost four times farther out than Pluto at the moment, in an elongated orbit that is currently calculated to be between 175 AU at its most distant and 27 AU at its closest. This perihelion distance puts the orbit inside that of Neptune, so we can technically call Farfarout a Trans-Neptunian Object. Team member David Tholen notes: A single orbit of Farfarout around the Sun takes 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.

Neptune turns out to have a huge influence on Farfarout, which is only about 400 kilometers across, making it small even for a dwarf planet. That thousand-year orbit constantly brings Farfarout close to Neptune, whose gravitational influence is substantial. This means that we cannot use Farfarout to help in the search for Planet X. That mysterious and as-yet-undiscovered planet can only be found using bodies that don’t gravitationally interact with any other large bodies (other than the Sun, of course), including Sedna and 2012 VP113. They may be closer in, but their orbits don’t come near Neptune, so any outer influence will come from Planet X. We think.

What’s also interesting here is that team member Chad Trujillo notes: 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. Farfarout will likely interact with Neptune again since their orbits continue to intersect.

These discoveries of distant solar system objects can only happen because our telescope technology has advanced to make it possible, with larger digital cameras on huge telescopes. This team is actively using this equipment to conduct a survey for more of these objects. They discovered that previous record holder, Farout, back in 2018. With the construction of even bigger observatories, we hope to get a complete picture of our solar system, and we’ll keep bringing you new discoveries as they are announced.

More Information

NAU press release

University of Hawai’i press release