Looking Up: The hunt for Planet X

We talked last week about the discovery of Pluto, and how astronomers had been looking around to find a ninth planet based on then-unexplained gravitational influences on the orbits of Uranus and Neptune. When Pluto was discovered it was hailed as the explanation. But when more data came in and we realized that Pluto wasn’t as big as we thought, the hunt heated up again, at least until data from Voyager determined that the orbits were in fact, exactly as they should be. So finding Pluto was just a giant coincidence!

For a while, searching for Planet 9, or Planet X, as many call it, went out of fashion. But new data has emerged in recent years suggesting that Planet X may still be out there.

There are several small signs that may add up to a fairly big planet; scientists say that all these curiosities can be explained in one go if there is an undiscovered Planet X orbiting, and that they’d have to come up with a lot of different explanations for each if there isn’t. So things are a lot neater with a theoretical Planet X out there (and scientists like neat).

What are those signs? Well, in studying the movements of Kuiper Belt objects, small bodies out in that frozen wasteland beyond Pluto, astronomers have found that many of them are clustered together in a way that often signals they are following the orbit of a larger body. They also all have orbits that point in a certain direction, which could be another giant (supergiant!) coincidence or they’re being influenced by another large gravitational body. There are also other Kuiper Belt objects out there that orbit opposite to the rest of our solar system, like going the wrong way down a one way street, which could be explained by the orbit of Planet X.

Some researchers also point out that the gravity of Planet X could explain the curious tilt to the plane of our solar system, which is a mysterious 6 degrees off from the equator of the sun, where it should be.

Scientists believe that Planet X is about the size of Neptune, and orbits farther out than Pluto. It’s possible that Planet X is currently too far out for our current technology to spot, and that we’ll eventually find it when its orbit brings it back into range. After all, that’s the case with many of the dwarf planets we expect to find, including the recently-found Goblin, whose orbit around the sun takes 40,000 years and which will be out of sight from Earth for a good part of that time.

But some astronomers believe we’d be able to find it with today’s telescopes, though the planet is bound to be very faint being so far out from the sun, and they are actively searching the skies in the hopes of getting to give Planet X an official name by discovering it.

Astronomers are also wondering if the discovery of a new planet might explain a few other funny things about our solar system. For example, in studying a number of other systems, we’ve realized that the most common type of world in orbit around other stars are types of planets which have been dubbed “super-Earths.” These planets are bigger than Earth but smaller than Neptune, and are conspicuously lacking from our own solar system. Current estimates of Planet X’s size would place it squarely in the super-Earth category, and may shed additional light on why we don’t seem to have as many of those otherwise common types of worlds.

Or Planet X may simply be a rogue world wandering out there that was captured by the gravity of our sun. Guess we won’t know until someone spots it! If it really exists at all, that is.

Looking up this week: Jupiter will be low in the southwest sky, with Mars in the south, and Saturn right between the two. The moon is currently a waxing gibbous and will be full on Wednesday.

Let's block ads! (Why?)