ABY.F | X, Planet X

The Kuiper Belt, itself a mystery, is also home to an even bigger puzzle. Several Kuiper Belt Objects have unusual orbits, which makes scientists think there may be yet another large planet that exerts enough gravity to affect them.

In 2015, two astronomers in California, Konstantin Batygin and Mike Brown, announced that their research indicated that there could be a planet as big as Neptune (remember, that’s nearly four times as big as Earth) going around the sun in a very long orbit. Their prediction wasn’t based on anything ever seen by anyone. Instead, it was based on complex mathematical modeling and computer simulations.

What led them to believe that there could be something as big as a planet out in the Kuiper Belt in the first place? It’s largely because of six objects that form an unusual cluster, which they think must be the result of some large planet exerting a gravitational pull on them. Could this cluster be just a random occurrence? Sure—the odds of it are one in 15.000, but it’s still a possibility. And it’s not like a planet has never been predicted via mathematics before. Remember,  Neptune was also anticipated by mathematicians over 60 years before it was finally seen through a telescope.

Batygin and Brown call their object “Planet Nine,” but other scientists prefer “Planet X.” Whatever it’s called right now, it won’t get an official name until, and IF, it’s actually discovered. At that point, the person who makes that discovery will get to pick the permanent name. Of course, even that choice will have to be approved by the International Astronomical Union. Perhaps this could be the first planet not to be named after a Roman God?

So what’s the hold up? Why haven’t we been able to see this mysterious planet yet? Part of the problem is the tremendous distance. Not many telescopes are capable of seeing that far away, and those that are have a very narrow field of view. Imagine you have to find an object the size of a marble in your living room—now imagine you can only search for it by looking through a drinking straw. The main telescope being used to search for Planet X is the 8.2-meter Subaru Telescope on Mauna Kea, in Hawaii.

Not that the Subaru Telescope, built in 1992, is “a drinking straw.” On the contrary, it’s one of the largest and most powerful telescopes in the world, and it’s already had its fair share of discoveries, including an object called 2015 TG387 in October of 2015. This new discovery, likely a fairly small dwarf planet, supports the presence of Planet X.

Even though everything we know about Planet X is only hypothetical for the time being, we do have some ideas about what we think we’ll eventually find. It’s likely that it could have a mass about ten times that of Earth. We also think that it could orbit about 20 times farther from the Sun than Neptune, taking between 10,000 and 20,000 Earth years to make one full orbit around the Sun.

In fact, at its farthest point in its orbit, Planet X could be as far away as 600 to 1200 AU, which is actually well past the far edge of the Kuiper Belt and into the realm of the Oort Cloud, the subject of our next lesson.

It’s ironic that the newest planet might be discovered by the same person who “killed” a previous one. Mike Brown was part of the team that discovered Eris in 2005, which led to the realization that there are many worlds in the Kuiper Belt, and eventually to Pluto’s reclassification from planet to dwarf planet. Brown even wrote a book called “How I Killed Pluto.” This same team also discovered Sedna, the most distant object that we’ve found so far.

Sedna is part of the outermost reaches of our Solar System, which we’ll learn more about in the next lesson.