Buzz
In early January, it was revealed that there may be an enormous ninth planet residing far beyond Pluto, sparking a flurry of excitement within the scientific world. Although much remains unknown about this possible new addition to the solar system, it is already clear that it is incredibly massive—at least 10 times the size of Earth. The astronomers behind this discovery even gave it the playful nickname 'Fatty.' The fact that such a colossal object has remained hidden for so long serves as a reminder of just how little we truly know about our own solar system and how much more there is to uncover.
10. The Man Who Demoted Pluto Was Also Behind the New Discovery
You might not know the name Mike Brown, but you’re familiar with his work. In 2005, Brown discovered a Kuiper Belt object called Eris, which briefly looked like it might be classified as a planet. This sparked a debate about what constitutes a planet, ultimately leading to both Pluto and Eris being reclassified as dwarf planets. Brown became widely known for this, even publishing a book titled How I Killed Pluto (And Why It Had It Coming).
In an ironic turn, the scientist who stripped Pluto of its planetary status may now be responsible for adding a new planet to our solar system. Alongside fellow astronomer Konstantin Batygin, Brown published research in the Astronomical Journal showing that the peculiar movement of 13 trans-Neptunian objects—celestial bodies orbiting beyond Neptune—suggests the presence of a massive, far-off planet: 'We realized that the only way we could get the [trans-Neptunian objects] to all swing in one direction is if there is a massive planet keeping them in place.'
Pluto’s exclusion from the list of planets has been a point of contention for many space fans. Hopefully, the discovery of Planet Nine can offer them some much-needed closure.
9. It’s An Ice Giant
In contrast to Pluto and Eris, both Brown and Batygin believe that Planet Nine qualifies as a true planet. Brown even shared with the New Yorker that this potential new planet 'would be more of a planet than anything else in the solar system.' According to him, 'what we now call planets are objects that can gravitationally dominate their neighborhood. Pluto is a slave to the gravitational influence of Neptune.' In terms of area, Planet Nine exerts more influence over the solar system than any other known planet—its very existence is inferred because of this dominance. Additionally, we’re fairly confident it’s not a small object: its mass is at least ten times that of Earth and five thousand times greater than Pluto’s.
Its estimated size also provides insights into its physical properties. The larger a planet, the thicker its atmosphere, due to a process called core accretion, in which it gathers more gaseous elements. This process is why rocky planets like Earth and Mars can only grow so large before transitioning into gas giants, like Jupiter and Saturn. Ice giants, however, represent a middle ground: their atmospheres are dense and similar to those of gas giants, yet they are far smaller in size.
The size of Planet Nine, which is larger than any rocky planet yet smaller than any gas giant, suggests it might belong to this unique classification. Scientists are still divided on the formation of ice giants, as many existing models present challenges when applied to more widely accepted theories about the formation of gas giants. As a result, ice giants continue to be a point of intense discussion within the scientific community, and the confirmation of Planet Nine could unlock a wealth of new data about these planetary enigmas.
8. It’s Incredibly Far Away
In astronomical terms, Planet Nine is astonishingly distant—its average distance from the Sun is 56 billion miles, more than 20 times the distance from the Sun to Neptune, the outermost planet we currently recognize. To put it into perspective, NASA’s New Horizons probe, which took nine years to reach Pluto, would have required at least 54 years to reach Planet Nine. And that’s under the best conditions, calculated for Nine’s closest approach to the Sun. Reaching Nine during its farthest point in orbit could take up to 350 years. These figures, however, are purely hypothetical, as New Horizons lacks the necessary fuel to make the trip.
This vast distance might help explain why Planet Nine has remained undetected for so long. According to Mike Brown and Konstantin Batygin’s calculations, their proposed planet could actually be seen with most backyard telescopes—if its orbit ever brings it closer to Earth. Since nobody has yet spotted Planet Nine from their backyards, it’s safe to assume it’s currently in a more distant part of its orbit, although Brown and Batygin maintain that it should still be detectable with extremely powerful observatory telescopes.
7. It Takes An Astoundingly Long Time To Orbit The Sun
Before you rush out to get a backyard telescope in the hopes of spotting Planet Nine anytime soon, be warned: the time it takes for this proposed planet to complete its orbit is still uncertain. However, Brown and Batygin estimate that it would take a minimum of 10,000 years. And that’s a cautious estimate—given its extreme distance from the Sun and its slightly tilted, elliptical orbit, it could take as long as 20,000 years for Planet Nine to finish a single lap around the Sun. If true, this would make it the planet with the longest orbital period in our solar system.
As is common with astronomical distances, the numbers involved are so immense that it’s hard to fully grasp their significance. To give you some perspective, if the lower estimate of 10,000 years is correct, the last time Planet Nine was where it is now, woolly mammoths still roamed the Earth, and the human population was only about five million. In the span of a single year on Planet Nine, the entire history of humanity—from the birth of agriculture to the invention of the iPod—could have unfolded. With seasons lasting centuries, it sounds surreal, but in a solar system where some planets have days that last longer than their years, it starts to make sense.
6. It May Have Once Been Much Closer
Planet Nine’s extreme isolation makes it stand out in every sense. Its incredible distance from the rest of the solar system makes everything else look like a tiny, close-knit community, with Planet Nine playing the role of the eccentric hermit living deep in the wilderness. However, it might not always have been this way, and as often happens, we can likely blame Jupiter, the solar system’s resident powerhouse.
In 2011, scientists began questioning why our solar system didn’t seem to have a fifth 'giant' planet, a feature common in many other systems. One theory is that Jupiter might have captured this missing giant in its powerful gravitational grip when the solar system was still young. The result? The unfortunate planet would have been ejected from the Sun’s orbit and cast out into the furthest corners of the solar system. While we can’t say for certain that Planet Nine was that lost fifth giant, its discovery in the far reaches of the solar system certainly supports this idea.
5. It Could Play a Role in Interstellar Travel
Space is vast, overwhelmingly vast, and one of the biggest challenges for interstellar travel is the simple fact that we don't have enough fuel to make the journey in any reasonable timeframe. After all, in the endless expanse of space, there are no gas stations or places to refuel. However, Planet Nine might hold the key to solving this problem. Just like how the Apollo 13 astronauts used the Moon’s gravity to slingshot themselves back to Earth, future explorers could use Planet Nine’s immense gravitational pull to accelerate their spacecraft, sending them further into space. This technique, called 'gravity assist,' has been successfully used by NASA before with spacecraft like Voyager and New Horizons, which used Jupiter’s gravity to speed up. We could potentially do the same with Planet Nine.
Well, that’s the theory anyway. Planets like Jupiter orbit relatively quickly, which allows NASA to time their gravity assist maneuvers to launch spacecraft in the right direction. But Planet Nine’s orbit, which spans 10,000 years, means it stays in roughly the same position for hundreds of years. This could limit its usefulness to certain directions, and may not align with where we want to go. Furthermore, if Planet Nine is a low-density planet like Neptune, the gravitational boost from a slingshot would be modest. Still, it’s an option worth exploring as we learn more about this distant planet.
4. Some Conspiracy Theorists Are Claiming It Could Be a Sign of the End Times...
It seems like every time something new is discovered in our solar system, conspiracy theorists eagerly declare it a potential sign of impending disaster. Asteroids, in particular, often take the spotlight, with claims that ones like Apophis, TV135, and 2014 YB35 are all on a collision course with Earth, threatening to wipe out humanity.
Planet Nine is no exception. Almost as soon as it was discovered, doomsayers on the Internet jumped to conclusions, claiming that it was actually Nibiru, or Planet X (a joke that doesn't quite hold up now that Pluto has been relegated to dwarf planet status). According to these conspiracy theorists, Nibiru is a mythical 'planet of doom,' long hidden by the powers that be, and will one day come dangerously close to Earth, causing catastrophic earthquakes and tsunamis with its gravitational pull.
Granted, it's not entirely clear how Planet Nine could cause such chaos from its distant orbit in the farthest reaches of the solar system, but who’s letting science get in the way of a good conspiracy theory?
3. But It’s Likely True
That being said, the probability that the orbital clustering of distant objects is a mere coincidence is estimated at just 0.007 percent. So far, there’s nothing else in the solar system with enough mass to explain these gravitational effects. This doesn’t guarantee Planet Nine’s existence, but scientists have yet to come up with any credible alternative explanations. As astrophysicist Chris Lintott told the Guardian, Brown and Batygin’s theory offers 'the most detailed and most convincing analysis' of any such hypothesis so far.
As this article is being written, new discoveries are continuing to emerge. Batygin and Brown are already predicting that there are more unseen objects out there, too distant to be detected by traditional methods, yet still orbiting the Sun. Even if Planet Nine turns out to be a non-existent myth, the excitement it has stirred up will remain an amazing reminder of the awe and enigma that space holds.
2. It Might Not Even Be Real!
Before we get too carried away and start sending Matt Damon to the Kuiper Belt, let’s keep things in perspective. As of now, Planet Nine is the most plausible explanation for the strange clustering of icy bodies beyond Neptune’s orbit. However, even the astronomers who proposed it are being cautious and tempering expectations. Mike Brown himself has suggested that the clustering could simply be an astonishing coincidence.
In fact, astronomy has a history of remarkable coincidences. At the dawn of the 20th century, Percival Lowell theorized that Neptune’s orbit was being influenced by an unseen giant planet. In 1930, Clyde Tombaugh discovered Pluto exactly where Lowell had predicted. But by the 1970s, astronomers discovered that Pluto was actually far too small to have any significant effect on Neptune’s orbit. It turned out that Lowell’s calculations had been based on faulty data, and the placement of Pluto was merely an incredible coincidence.
As thrilling as the idea is, it’s important to remember that Planet Nine has yet to be observed, and there’s still a chance it might not exist at all.
1. ...And There’s A Very Small Chance They Could Be Right
Some of the more thoughtful doomsayers suggest that Planet Nine’s gravitational influence could send asteroids hurtling towards Earth, leading to potentially catastrophic impacts. Scientifically, this theory holds more weight: the gravitational influence of Planet Nine (or whatever it may be) is well documented. After all, it was the observed effects of this gravity well on distant rocky bodies that led to the hypothesis of Planet Nine. So, there’s a chance that one or two of these objects could be redirected toward Earth.
However, it’s still not all that probable—remember that space is overwhelmingly vast. Even if an object was deflected into our region, it would still have to hit Earth, instead of drifting aimlessly through the endless void. It’s possible, but far from certain. Astronomer Scott Sheppard noted that Planet Nine could “send a few small objects into the inner solar system from time to time, but [won’t] significantly raise the odds of a mass extinction event.”
