Some scientists hypothesize that a mysterious, gigantic 9th planet may be lurking at our solar system’s edge. Why haven't we seen it yet?

Over the past century, astronomers have speculated about the existence of a mysterious 9th planet lurking in the outer reaches of our solar system.

Although we’ve never directly observed the elusive Planet X, researchers keep finding more strange phenomena that seem to support its existence. Scientists believe that Planet X, also referred to as Planet 9, is about 17 times bigger than Earth, and made entirely out of gas.

You’d think it would be easy to spot something so big, but it orbits the sun about 10 to 20 times farther away than Pluto. Finding this planet would teach us more about how solar systems evolve, but could it also bring about the end of days?

So far our hunt for Planet X has been mostly based around the idea of if there’s smoke, there’s fire. And in this case, the smoke is a bunch of weird things going on amongst the stars.

In 1972, astronomers noticed some irregularities in the course of Hailey’s comet; detours that they figured were caused by the gravitational pull of an unseen, distant planet.

Fast forward ten years to 1982, when scientists were once again forced to consider the existence of a hidden planet. They hypothesized that an unknown, outer planet could be orbiting within our solar system, and causing the orbits of Uranus and Neptune to deviate from the laws of physics.

But the most concrete evidence came in 2014, when astronomers noticed some distant dwarf planets and icy objects that all seemed to follow orbits that cluster together.

Upon closer inspection, they estimated that the powerful gravitational pull of a hidden planet must’ve been the cause of these unusual orbits.

So with all these signs pointing to the existence and location of Planet X, why haven’t we been able to see it yet? Well, it’s really, really far away, and out in space things get dark pretty fast. The intensity of the sunlight weakens by a factor of four going out, and then four times again reflecting back.

To put that in perspective: a planet that’s twice as far away as our moon would be 16 times fainter. On top of that, the planet could be lost in the light pollution of the Milky Way, or the glare of a bright star.

But with modern technology, astronomers believe we’ll be able to find Planet X in 10 to 15 years. The leading team in California uses one of the most powerful telescopes in the world and has released a map of where to look to increase the chances of finding it through crowd-sourced astronomy.

If Planet X is real, it would redefine our knowledge of our solar system’s evolution, and give us key insights into how other solar systems are formed throughout the universe.

For as long as serious scientists have been looking for Planet X, there have been others who have proclaimed that its strange orbit will eventually collide with Earth.

But this has been rejected as nothing more than pseudoscience, and an internet hoax. Scientists say that Planet X would be kept well beyond Neptune throughout its orbit, even when it’s closest to the sun.

So even though we can’t see it, doesn’t mean our 9th planet isn’t there. Maybe one day we’ll develop technology that can identify worlds even further out than Planet X.