330 kilometer wide "plutonic world" behind Pluto, but on a stable orbit, making it "not-asteroid" seems to be relic from 400 million years ago
https://www.sciencealert.com/strange-fossil-world-detected-at-fringes-of-solar-system
The weird elongated orbit of the newly found small object suggests that if "Planet Nine" exists, it is much further from the sun than thought, or it has been ejected from our planetary system altogether.
>Planet Nine would be about half the size of Neptune, so bigger than Earth
>After 20 years of search there is still no proof of planet Nine, but several small objects have been found behind Pluto, none of them bigger than Pluto (Pluto is smaller than Earths moon)
The strange orbit of the object, designated "Ammonite," classifies it as a "sednoid." Sednoids are bodies beyond the orbit of the ice giant Neptune, known as trans-Neptunian objects (TNOs), characterized by a highly eccentric (non-circular) orbit and a distant closest approach to the sun or "perihelion." The closest distance that Ammonite ever comes to our star is equivalent to 71 times the distance between Earth and the sun...
The team behind the discovery, made using Subaru Telescope as part of the Formation of the Outer Solar System: An Icy Legacy (FOSSIL) survey, thinks that
>all four known sednoids were on similar orbits around 4.2 billion years ago.
However it is no longer so.
That implies something dramatic happened out at the edge of the solar system around 400 million years ago.
