Rendering of hypothetical view from Planet 9 back towards the sun. The object is thought to be gaseous, similar to Uranus and Neptune. Image Credit: NASA/Caltech/R. Hurt (IPAC)
Many scientists believe that there is another massive planet in our solar system, way out beyond Pluto. They call it Planet 9 (Planet X if you’re a proponent of Pluto’s full planetary membership); a planet they think may be 10 times more massive than Earth. And, they’ve recently locked down the orbit of another object that supports that theory. It’s affectionately called The Goblin (2015 TG387), and it’s got an interesting story to tell.
The Goblin is a clue. Study leader of the Carnegie Institution for Science, Scott Sheppard said in a statement, “These distant objects are like breadcrumbs leading us to Planet X”. The reason for that is gravity. The theory is that this large planet of great mass is “shepherding” other, smaller bodies around the sun with its gravitational pull. Scientists expect that Planet 9 exists precisely because these other objects are following similar patterns of orbit that would necessitate a larger body’s assistance.
Shepard and his colleagues estimate that The Goblin is approximately 186 miles in diameter and “probably spherical”, according to space.com. Those two things would qualify The Goblin as a dwarf planet like Pluto. Sorry, Pluto.
The Goblin travels on an extremely elliptical path in its orbit. But, the orbit is the thing. The Goblin and other far-flung objects (Sedna and 2012 VP113) in the solar system are clustered in same part of the sky during the elongated part of their orbits, which suggests that they’re being guided along by something much bigger. Sheppard believes the odds of Planet 9’s existence is at around 85 percent.
So, how is it that no one has gotten a look at the mysterious Planet 9? Especially if it’s as big as they think? Well, it’s very very far away. They think that Planet 9 may orbit the sun at around 600 astronomical units (AU) on average. To give you some perspective, Earth orbits the sun at 1 AU (about 93 million miles) on average. Pluto never gets closer to the sun than 29.7 AU, or farther away than 49.3 AU. And, The Goblin comes within about 65 AU of the sun at its closest point and gets about 2,300 AU away at its most distant. It takes The Goblin about 40,000 Earth years to orbit the sun.
Planet 9 is too far away for us to see with our current equipment. If it’s there, it’s too faint to detect. That’s not to mention, we don’t know exactly where to look and the sky is so very vast. As Sheppard put it, “You can hide a very big thing in the outer solar system very easily.”