According to a paper published in the journal Nature in 2014 by Scott Sheppard and Chad Trujillo of the Gemini Observatory in Hawaii, “a massive outer Solar System perturber may exist.” What exactly are they referring to and what does that mean?
Well, there is an orbital feature known as ‘the argument of perihelion.’ It refers to the angle at which an object comes to perihelion as it pertains to the ecliptical plane.
No? Okay, try this. A huge object would disturb anything in the same neighborhood. (Obviously objects that stay away from such disturbances are the most stable. So what Scott & Chad are saying is that there is likely a reaction in the area behind Pluto that would best be explained by a perihelion orbit (the sort of orbit that tends to keep the smaller objects from the bigger.)
To date, astronomers have discovered 1500 chunks of ice out in the Kuiper belt – some of them qualify for Dwarf planet status. BUT the object that is hinted at behind Pluto is Neptune sized.
Yes, we are currently still discovering objects – planets and hunks of rock & ice. Technology, more sensitive equipment, helps, even more sensitive would be great. Basically this Planet X is out there, it's very far away and likely quite faint likely in at least 200 Astronomical Units from the Sun (meaning 200 times farther from the sun than is the Earth.)
How would a planet, theorized to be as large as Neptune have ended up way out there? Long ago the planet would have formed closer to the sun and maybe it formed similar to a planet such as Jupiter or Saturn. But then it was ejected toward the outer solar system through gravitational interactions with other giant planets.
Now while I hate it when scientists and the like spout of theories and thoughts based on little fact; if one were to visit this gloomy, cold world, what would it be like? That one is actually easy – big & cold. It would resemble a snowball.
Anybody want to ski the outer solar system?
**And now, since I brought up the fact that likely its Neptune size, this planet X, here are some fun facts about Neptune.