We used to think we had a pretty good picture of the solar system. There were nine planets and Pluto was a bit weird, but it was undeniably a planet. Then we discovered other Pluto-like "trans-Neptunian objects" (TNO) and scientists began to re-evaluate what it means to be a planet. Pluto was demoted and astronomers turned their attention to the confines of the solar system in search of distant and icy planoids. Last year, astronomers from the Carnegie Institution for Science spotted the dwarf planet furthest away so far, called FarOut. FarOut can now move – FarFarOut is even further away.
The first image of FarFarOut comes from Scott Sheppard, the astronomer of the Carnegie Institution, who also spotted FarOut last year. FarOut was already far enough at 120 AU (1 AU or astronomical unit is the distance between the Earth and the Sun), or nearly 20 hours of light. The first observations of FarFarOut suggest that it is about 140 AU. Pluto is only at 34 AU and the most distant dwarf planet known as Eris is at 96 AU.
Sheppard announced the discovery of FarFarOut at a conference last week, after reading his team's data the day before. The first image showing FarFarOut came from the 8-meter Subaru telescope in Mauna Kea, Hawaii, which was barely powerful enough to detect it. Based on distance and brightness, Sheppard estimates that the object is a dwarf planet about 400 kilometers (248 miles) in diameter.
Additional observations over several months or years will be required to determine the exact orbit of FarFarOut. It is so far away that a single solar year for the dwarf planet represents more than 1,000 Earth years. We do not know what it looks like – it's technically a FarOut representation at the top, but it does not matter, we're just guessing it. More researchers will have to confirm the results before we can be sure that FarFarOut is really there. Only then can we give it a name – it does not have a minor planet designation yet.
The Carnegie Institution team is actually accumulating these discoveries of the dwarf planet, but that is not why it scrutinizes the limits of the solar system. Sheppard and his colleagues are looking for larger planets similar to Earth in the outer solar system. This theorized "New Planet" could explain some of the orbital oddities observed in the NWT. It is also possible that there is no Planet Nine, and the grouping of TNO orbits is simply the product of the cumulative gravity of many objects like FarFarOut. In both cases, the discovery of dwarf planets is still impressive.