Does planet X guide dwarf planets around our solar system?

This visualization compares the orbits of "The Goblin" and other similar objects.
(Credit: Illustration by Roberto Molar Candanosa and Scott Sheppard, courtesy Carnegie Institution for Science)

Astronomers have discovered a dwarf planet beyond Neptune called "The Goblin" because of its initial discovery around Halloween. The Goblin, officially named 2015 TG387, joins other small distant objects from our solar system, and adds to a tantalizing theory about another much more massive "Planet X" hidden beyond Neptune.

Goblin's journey

Carnegie's astronomer Scott Sheppard researches and studies distant objects such as The Goblin. In recent years, they have noticed something interesting about the motley group of smaller bodies that surround the confines of our solar system. Although you expected their orbits to be random, Sheppard says that they all seem to be in harmony with each other. The planetary dance is a clue that something with a much greater gravitational attraction is guiding them – Planet X.

"Finding all these objects in a similar place," explained Sheppard, "suggests that there is a great planet out there that guides the goblin and other objects."

Although researchers do not know what Planet X's orbit looks like, they have an idea, Sheppard explained. His research team performed on-orbit simulations, and The Goblin fits in perfectly.

If you randomly place a planet as gigantic as Planet X in the outer solar system, such a planet "would make the goblin's orbit unstable, so you'd expect it to be ejected from the solar system." Sheppard said. The stability that the team has found in the simulations means that the two objects will never approach or threaten to collide, which would explain why we are seeing The Goblin today.

So, by discovering The Goblin, this team has found more evidence of the existence of Planet X and more information about what this planet could be. Sheppard and her team will continue to scour the night sky for other items like The Goblin – smaller prizes that might one day help them put the big one.