I think we might have to take it with a pinch of salt until they actually detect it. Stories of a ninth planet (or a tenth before Pluto was demoted) have come up periodically but the thing I find not entirely convincing is that one of the furthest objects detected in the solar system is Sedna, which has a similarly egg-shaped orbit and was imaged at a distance roughly as far away as the hypothetical ninth planet.
So how can they image an object as small as Sedna (roughly 700 miles in diametre) but so far not have spotted a planet the size of Neptune orbiting at roughly the same distance?
They' ve been looking for it for nearly a century The Pits ! Ever since they discovered Pluto and realised Pluto was nowhere near massive enough to account for Neptune's orbital perturbations they've been looking for a "planet X". Then they found that Neptune is not after all affected by any perturbations and the idea that was had been the result of miscalculations.
Now they're saying that something massive must be perturbing the orbit of far-flung objects in the outer Kuipper Belt or Oort cloud. So there might be another planet way out there but they're also saying there might be an alternative explanation so we can't be sure of anything until they actually spot it.
Probably because space is quite large and a planet the size of Neptune is relitively small. I bet it's like looking for a needle in a hay stack if the needle is microscopic, the hay stack is the size of Asia, and you have to do it at night with no flashlight.
If the planet were dark it would be nearly invisible against the blackness of space. Depending upon its makeup, particularly that of its core, it might be only a few degrees Kelvin, making even thermal imaging almost impossible.
I doubt that they have been able to calculate the orbital plane it would occupy. You cannot assume it to be the same as that of the other planets. That far out, it could be a "captured" planet, which would make virtually any orbital plane possible, further complicating the actual finding of the planet.
I don't care how dark, or cold, or how long it takes to orbit. If they come out and announce that we've got another planet in our Solar System then we as humans can just throw our hands up and say we don't know jack-shit about Space.
OK so they have made an off the cuff calculation of how long it would take to orbit the Sun, if in fact planet 9 is really there. Who knows, but it's still fascinating.
If it is a captured planet, which system is it captured from ? How far away is the nearest solar system ? I can understand captured moons within our solar system , or comets/asteroids being flung out of orbit. Even planets being flung out of solar systems. But they just lurk out in interstellar space, it's a very long way from here to anywhere out there.
Or if it does exist it could be a planet that originated for closer to the sun but was flung out onto the outer edges of the solar system early on in its history by the gravitational tug-of-war of the cosmic dance of its two giants Jupiter and Saturn.
With more mass than everything else combined (apart from the sun itself) it's Jupiter that decides what happens in the solar system. Drawing stuff in, pushing it out, and prime architect of planet migration.
Just as a complete aside, there was an interview with an astrophysicist on R4 the other day who was asked "if the universe is expanding what is it expanding in to". His/her answer was, "nothing". I got mildly annoyed as for something to expand it must have something to expand in to. The universe we are in can't just exist in glorious isolation, outside of which there is nothing.
I suppose it avoid the question of whether there is a god/God.