Here's one capability explanation why the body remains elusive despite circumstantial proof that it exists beyond planet Neptune.
The case for Planet Nine now focuses on the belief that something beyond Neptune that is causing the orbits of other space objects to be affected.
Although it might be too hard to spot because of the distance, astronomers are convinced that there is an extra planet inside our solar system.
The existence of Planet Nine is not official yet, although there are plenty of esteemed scientists and astronomers that have strong suspicions about a large planet just lurking on the outskirts of our solar system. Planet Nine, is believed to be 10 times bigger than Earth and 20 times farther out from the sun than Neptune - the outer-most planet in the solar system.
"There are now five different lines of observational evidence pointing to the existence of Planet Nine", Konstantin Batygin, a planetary astrophysicist at Caltech in Pasadena, California, had said in the NASA 2017 press release. If Planet Nine is now at a distant point in its orbit, it could take thousands of years for it to circle back to a point where it's visible from Earth.
Scientists think that the existence of this world could explain the strangle looping of the trans-Neptunian objects (TNOs) at the edge of our star system. Nevertheless, scientists still believe there is a possibility of that planet existing and being "10 times the mass of Earth". The challenge is that the planet is thought to be so dim, about a million times dimmer than Neptune, that it could hide in the light pollution from the Milky Way.
Scott Shepherd, an astronomer at the Carnegie Institution for Science in Washington, explained: "If things are in the same orbit, then something's pushing them".
Is there are mysterious planet out there that we can not see?
This means that our millimeter telescopes in Antarctica and Chile might be able to pick up its glow if Planet Nine happens to cross their search field.
The worst-case scenario is that we might glance over to its location when the planet has already moved to a more distant point in its elliptical orbit, slipping beyond the 1,000 AU-limit.