FarFarOut Might Be the Most Distant Object in the Solar System

We used to think we had a pretty good picture of the solar system. There were nine planets, and Pluto was a little weird, but it was undeniably a planet. Then, we discovered more Pluto-like “trans-Neptunian objects” (TNOs), and scientists started to reevaluate what it means to be a planet. Pluto was demoted, and astronomers turned their attention to the outer reaches of the solar system in search of distant, frigid planetoids. Just last year, astronomers from the Carnegie Institution for Science spotted the most distant dwarf planet yet, dubbed FarOut. Now, FarOut can move over — FarFarOut is the even farther away.

The first image of FarFarOut comes from Scott Sheppard, the Carnegie Institution astronomer who also spotted FarOut last year. FarOut was already quite distant at 120 AU (1 AU or astronomical unit is the distance between Earth and the sun), which is almost 20 light hours. Initial observations of FarFarOut suggest it’s about 140 AU away. Pluto is a mere 34 AU away, and the most distant dwarf Planet known as Eris is at 96 AU.

Sheppard announced the discovery of FarFarOut during a lecture last week, having perused his team’s data the previous day. The initial frame showing FarFarOut came from the Subaru 8-meter telescope on Mauna Kea in Hawaii, which is only barely powerful enough to detect it. Based on the distance and brightness, Sheppard estimates the object is a dwarf planet about 400 kilometers (248 miles) in diameter.


Pluto, the first dwarf planet.

It will take additional observations over months or years to determine FarFarOut’s exact orbit. It’s so far away, a single solar year for the dwarf planet is over 1,000 Earth years. We don’t know what it looks like — that’s technically a depiction of FarOut at the top, but it doesn’t matter since we’re just guessing at that, too. More researchers will need to confirm the findings before we can even be sure FarFarOut is really there. Only then can we give it a name — it doesn’t even have a minor planet designation yet.

The Carnegie Institution team is really racking up these dwarf planet discoveries, but that’s not why it’s scanning the edge of the solar system. Sheppard and colleagues are looking for larger Earth-like planets in the outer solar system. This theorized “Planet Nine” could explain some of the orbital oddities seen in TNOs. It’s also possible there is no Planet Nine, and the clustering of TNO orbits is simply a product of the cumulative gravity from numerous objects like FarFarOut. In either case, discovering dwarf planets is still pretty impressive.

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