With the discovery of a new dwarf planet, which is officially called 2015 TG387 but scientists are referring to as "The Goblin", evidence for a ninth planet is mounting. Remembering, of course, that Pluto was relegated to dwarf planet status back in 2006, the solar system currently has eight planets (although that is still being hotly debated).
Lead by Scott Sheppard, a team of scientists out of the Carnegie Institution’s Department of Terrestrial Magnetism announced the discovery second farthest known object in the solar system. Like their previous discoveries, the Goblin has a highly elongated orbit which they hypothesize to be affected by a massive, currently undiscovered planet lurking deep in our solar system.
Taking 40,000 years to orbit the sun, the Goblin's closest approach is 65 AU. One AU is the mean distance of the earth from the sun. The Goblin's farthest distance from the sun is a whopping 23,000 AU. For reference, Pluto's orbit ranges from 39.5 AU to 27.9 AU.
Two other known objects, Sedna and 2012 VP113, have extreme orbits like the Goblin's, travel in the same part of the sky and their orbits seem to be influenced very little by the rest of the solar system. As such, theory is that there could be a distant celestial object, namely a planet, tugging on their orbits.
Sheppard estimates the odds of an additional planet existing at 80 to 85%. Konstantin Batygin, one of the two astrophysicists who published a now well known paper arguing the case for Planet 9, puts the odds at precisely 99.84 percent.
Of course, not everyone agrees that these objects are being pulled by another planet. In fact, there are a number of different hypothesis as to what is causing their unusual orbits. But they all agree that something is causing this, whether it be a past celestial encounter or there simply being enough minor planets that they all have gradually pushed each other's orbits.
If Planet 9 is out there, it could be way out there. Something like 1,000 AU from the sun. It's believed the planet is between 2 and 4 times the size of earth. At that distance and that size, the body would be incredibly difficult to detect. In fact, the only reason the Goblin was discovered is because it's nearing its closest approach to the sun. With that in mind, there could be many other minor planets in that very same part of the sky.
The jury is still out and to many astrophysicists the odds are long but as Shepperd says, “Once a century we find a planet, right? So, it’s time to find one again."
Check out the full article at: https://www.smithsonianmag.com/science-nature/new-discovery-goblin-stirs-signs-elusive-planet-9-180970442/