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‘Farfarout’ Confirmed Far Beyond Pluto

One thing is certain about the now confirmed object that is being described as the most distant ever observed in our Solar System. We’ll just be getting used to using the official designation of 2018 AG37 (bestowed by the Minor Planet Center according to IAU protocol) when it will be given an official name, just as 2003 VB12 was transformed into Sedna and 2003 UB313 became Eris. It’s got a charming nickname, though, the jesting title “Farfarout.”

I assume the latter comes straight from the discovery team, and it’s a natural because the previous most distant object, found in 2018, was dubbed “Farout” by the same team of astronomers. That team includes Scott Sheppard (Carnegie Institution for Science), Chad Trujillo (Northern Arizona University) and David Tholen (University of Hawaiʻi). Farout, by the way, has the IAU designation 2018 VG18, but has not to my knowledge received an official name. Trans-Neptunian objects can be useful for investigating the gravitational effects of possible larger objects — like the putative Planet 9 — deep in the reaches of the system.

Image: Solar System distances to scale, showing the newly discovered planetoid, nicknamed “Farfarout,” compared to other known Solar System objects, including the previous record holder 2018 VG18 “Farout,” also found by the same team. Credit: Roberto Molar Candanosa, Scott S. Sheppard (Carnegie Institution for Science) and Brooks Bays (University of Hawaiʻi).

As to Farfarout, it turned up in data collected at the Subaru 8-meter telescope at Maunakea (Hawaiʻi) in 2018, with observations at Gemini North and the Magellan telescopes (Las Campanas Observatory, Chile) helping to constrain its orbit. Its average distance from the Sun appears to be 101 AU, but the orbit is elliptical, reaching 175 AU at aphelion and closing to 27 AU (inside the orbit of Neptune) at its closest approach to the Sun. That makes for a single revolution about the Sun that lasts a thousand years, and a long history of gravitational interactions with Neptune.

Farfarout is thought to be about 400 kilometers in diameter, making it a very small dwarf planet, though this would depend on interpretations of its albedo and the assumption that it is an icy object. In any case, its gravitational dealings with Neptune over the course of the Solar System’s history affect its usefulness as a marker for detecting massive objects further out. For that, we turn to objects like Sedna and 2012 VP113, which do not approach Neptune.

On the other hand, the Neptune interactions can be useful, as Chad Trujillo points out:

“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 strongly interact with Neptune again since their orbits continue to intersect.”

Image: An early estimate of Farfarout’s orbit. Credit: By Tomruen – JPL [1], CC BY-SA 4.0.

We’re at the early stages of our explorations of the outer system, and it’s safe to assume that a windfall of such objects awaits astronomers as our cameras and telescopes continue to improve. Sheppard, Tholen and Trujillo will doubtless turn up more as they continue the hunt for Planet 9.

{ 15 comments… add one }
  • Geoffrey Hillend February 12, 2021, 16:36

    It’s right on the line of being dwarf planet which is 400 km. I wonder if it is round?

    • Robin Datta February 13, 2021, 8:22

      There will be an ample supply of far-flung bodies for colonization and meterial extraction. Ambient radiation may be ameliorated by burrowing under the surface. Those who might choose to live out their time in such places may count the passage of their lives in earth years: it would take many generations to complete one year of such a body.

    • Andrei February 14, 2021, 4:16

      They’ve observed it in the last couple of days, and possibly ongoing analysis might give us a better estimate of the size, rotation and shape.
      But yes, it’s indeed on the fence to be considered a dwarf planet, so the shape might become the deciding factor here.

  • Thomas Mazanec February 13, 2021, 11:05

    The average of 27 and 175 is 132?

    • Paul Gilster February 13, 2021, 11:47

      101. Clumsy fingers at this end, evidently. Or maybe my speed typing is outrunning my thinking…

    • Robin Datta February 13, 2021, 17:44

      “The average of 27 and 175 is” a helluva lot more than would make Earth’s biota comfortable, myself included. Especially when the units are AU.

  • Greg L February 13, 2021, 18:38

    There already is a Planet 9. It’s called Pluto. :-)

    • Thomas R Mazanec February 14, 2021, 10:10

      Then Ceres is planet 5 and Pluto is Planet 10.

      • Mike Serfas February 14, 2021, 16:41

        Politics is about compromise. 9 1/2? :)

        • ljk February 17, 2021, 13:05

          Pluto and Ceres and any other objects similar to them in size and composition should be made into a new planetary status. Have we not learned by now with over four thousand known exoworlds that there are more than just two types of planets?

          • Astronist February 23, 2021, 11:28

            Why not call them “dwarf planets”, by analogy with “giant planets”?

  • jonW February 14, 2021, 13:16

    Just wondering about the possible future interactions with Neptune: are there plausible orbital interactions that result in a smaller body’s orbit being made *less* eccentric? It seems like whenever I hear about interactions with a larger body, the smaller body gets “flung out”. How likely is it that Farfarout could be brought back into the fold instead through its interaction with Neptune?

    • Ivar Brouwer February 15, 2021, 11:59

      Think Triton (even though that probably required 3 body’s)
      It seems unlikely that Neptune would capture it, and loss of momentum is far less likely then gaining it.
      As the angle of approach to Neptune would be relatively low, but the momentum high, therefore the chance on a less extreme orbit is probably smaller then the other way around, a round orbit unlikely because the exit would be different from the approach angle.
      Using my 3D imagination it looks more unlikely FarFarOut would be flung to the inner solar system.
      (It’s all a game of approach angles and speeds, but approach is most likely in the same direction, FarFarOut would I think being the quicker one, although more mass probably means more speed overall.. maybe therefore FarFar would be flung out in an more angled direction, but many scenarios are possible…)

  • charlie February 15, 2021, 0:23

    When they end up calling these “far-flung bodies”-is that really a fair designation? The reason I ask that is isn’t there comets which have periods of something like several million years? And how do we know that this particular object is not in fact a comet, but it’s just not able to get close enough to the sun to show a tail?

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