There was some stir about twenty years ago, when an international board of space scientists—including Neil DeGrasse Tyson, director of the Hayden Planetarium in New York City—demoted Pluto from its accepted role as a full-fledged planet, reducing the number of official orbs in our system from nine to eight. This upset a lot of people, myself included, but the decision was based on scientific principles and not done on a whim, or so they claimed. For years, as technology became increasingly sophisticated, we learned more and more about the former 9th world and the data did not support its continuing in the position. Disappointing as this might have been (and it certainly rankled) Pluto's journey from theory to discovery to its current status as a ‘dwarf planet’ has helped to fertilize the scientific community's imagination about another tantalizing possibility way out there in the outskirts of our solar system.
The scuttlebutt around the astronomer’s water fountain has been that there may be a potential ninth planet that fits all the standards of planethood lurking just beyond our ability to prove its existence. However fantastic that seems, I find the concept a fascinating distraction from the lasting frustration of Pluto's change from when I was a lad.
I admit, when the news reached me, I was sad and not a little concerned about the audacity of modern science. It made me feel like a well-known support structure had been removed and that science as I knew it would topple into pseudoscientific malarky. If they could remove a planet, what was next; declaring that only two of Newton's laws were up to scratch? The change was a lot to get used to.
Eastern Lebanon County (ELCO) Middle School had a planetarium and our space science teacher, Mr. Philips, drilled us on star names, the planets and constellations and rudimentary astrophysics during my seventh-grade year. It was the only class in my entire school career that I passed with no effort through sheer love of the subject matter. Within the parameters of the curriculum was the well-established fact that Pluto was the last little world out there at the border of our cozy star system. I always imagined a hand-painted sign affixed to a stake hammered into Pluto that read, “NOW LEAVING THE SOLAR SYSTEM. Y'ALL COME BACK!”
But Pluto no longer plays in the big leagues and sadly, there will be no chance for the tiny sphere to get called back up to the majors. By the standards of the other eight players in the system, Pluto is more akin to a very large asteroid or moon or a tiny remnant of the intervening chaos of the early formation of our star’s history than a planet. This reality is the price of scientific discovery. As we learn new things, we have to update our understanding.
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Aside from a handful of numbskulls that believe that the earth is flat or that the moon landing was faked, most people know that we live on a planet in the solar system named after our local home star, called Sol. The inner four terrestrial planets are rocky and small and only one has water and life (Earth). The others are not just hostile to Earth life, but barren of their own. While Mars appears to have supported life at some point in the distant past, it has since lost that ability. Mercury and Venus, on the other hand, have never been able to sustain life—Mercury due to its proximity to the sun and Venus due to its sultry atmosphere containing too much methane and ammonia.
Next come the massive gas giants, the first of which is the largest in our system, Jupiter. Between Mars and Jupiter, though, spins a huge ring of asteroids called the Main Belt. Astronomers have speculated about what this ring of asteroids may once have been. There are millions or even billions of asteroids whirling here, ranging in size from dust to the largest-known chunk, Ceres, which is about a quarter the size of our moon and half as big as Pluto. The asteroid belt might be leftover junk from the formation of the other planets, or it might be the remnants of a destroyed world.
Just past the Main Belt comes monstrous Jupiter. This Jovian behemoth is one-tenth the size of our sun and has upwards of seventy-nine moons, the four largest of which, Io, Ganymede, Europa and Calisto, were picked out by Galileo Galilei before he was put in prison for thinking too much about the planets and the star they orbit. Jupiter’s atmosphere is mainly hydrogen, helium and ammonia, but it is so thick that we cannot see what may be at its core. Jupiter is known for The Great Red Spot, a gargantuan storm that has thundered on for millennia.
Next is the second-largest gas giant, Saturn. Named after the Roman god of agriculture, this gigantic planet is known for its rings of rock and ice, which Galileo also discovered. Saturn has many moons, but Titan, the second-largest in the solar system, is the only moon with a thick atmosphere and, like Earth, the only planet with stable oceans, though they are liquid hydrocarbons (like oil). Both Saturn and Jupiter are the furthest planets in our system that are visible with the naked eye.
Beyond Saturn is Uranus, an ice giant with nine small rings. Uranus is pitched, so that its axis is horizontal and its rings seem to orbit vertically. Out beyond Uranus, is the last planet in the system, Neptune, a dark blue ice giant and the only current planet that was not discovered by empirical observation. Interestingly, Neptune has an almost perfectly circular orbit, unlike the elliptical orbits of the other planets and is therefore almost always the same distance from the sun at any time in its 164.8 year orbit. Neptune has sixteen moons, but only one, Triton, is spheroidal.
Beyond Neptune is the Kuiper Belt, named after the Dutch astronomer, Gerard Kuiper, who accurately predicted its existence. Dwarf planets, like Pluto, and “planetesimals” and asteroids and dust and remnants of methane, ammonia and ice revolve here in an ever-moving chaotic merry-go-round of space debris in a circumstellar ring. These Trans Neptunian Objects have wild and wooly orbits that cause them to careen around like unhinged rodeo clowns, swinging this way and that and bashing into one another. Beyond these whirling dwarf planets and large asteroids are the Extreme Trans Neptunian Objects (ETNOs) which reside at the farthest edge of our ability to know and observe.
The ETNos behave similarly to their nearer cousins, but sometimes they jut and wangle almost as if they are influenced by gravity beyond their own. They hunker and wobble and spin in strange clumps and arrays, almost exactly as they might if they were pulled on by a gas giant. This has caused speculation that they are actually being perturbed by massive gravity other than their own or Neptune’s. The ETNOs are, according to some theories, swarming and swirling because of the gravity of a giant planet out beyond them. A planet so far away that we cannot see it, but that is, essentially, still part of our solar system and just waiting to be discovered by more powerful instruments and sharper minds.
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In the late 19th Century, Percival Lowell, a somewhat misunderstood and ridiculed astronomer, echoed centuries of speculation when he claimed that there was a planet in the depths of the solar system, beyond Neptune. Well before the tools necessary to make such discoveries were developed, Lowell postulated that the gravitational behavior of Neptune and Uranus showed that there must be another planet out there. He called it Planet X. Lowell became obsessed with proving the existence of Planet X, motivated by his famously bad theory that had black balled him within the scientific community of his era. Lowell's other idea—that the lines on Mars were canals created by Martians—was heartlessly mocked. Both H.G. Wells and Edgar Rice Burroughs made use of this “pseudo theory” to enhance their fictional representations of Mars and Martians in their science fiction adventure novels, The War of the Worlds and the John Carter of Mars series, respectively. Desperate to live down the ridicule, Lowell worked tirelessly to prove Planet X was out there.
Lowell died suddenly in 1916 with Planet X unproven, but most of the work he left to prove that the mystery planet was there led to the discovery of Pluto in 1930. After his death, Lowell’s brother donated money to refit the telescope at the Lowell observatory in Flagstaff, Arizona with more powerful lenses. Over the next fifteen years, continuous photography of the night sky in the region where Lowell had suggested Planet X might be, led to the discovery of an object large enough to match the weird “perturbed” orbits of Uranus and especially Neptune. Planet X became Pluto.
That Lowell never lived to see his Planet X theory even partially vindicated is only half the tragedy. When the dwarf planet was originally assumed to be there, there was no way to truly measure its size or know much about it at all. For the next seventy years, though, with the advent of more powerful telescopes and more sophisticated technology, Pluto was almost continuously downgraded from Lowell’s original idea of Planet X to its modern reality. The International Astronomical Union (IAU) fired Pluto in 2006, 90 years after Lowell worked himself to death trying to find it. However the discovery of the tiny planet is very impressive considering the era and lack of technology.
Not only can we now see Pluto, thanks to powerful telescopes and modern computing, we can see its moons. The miniscule world has five, the largest of which, Charon, is just a little less than half Pluto’s size. The other four, Styx, Nix, Kerberos and Hydra (note the underworld theme) are merely chunks of rock caught in orbit around their dark father. We didn’t know about them until 2015 when the New Horizons spacecraft was able to fly by and take measurements and photographs. In 1992, it was discovered that Pluto was the largest of a massive number of other objects in the Kuiper Belt.
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Hard work, initiative and dedication to a theory discovered Pluto. It is hard not to think that a similar discipline will lead us to find the planet that could be causing gravitational upheaval beyond the ETNOs. The scientists suggesting a gas giant past the Kuiper Belt are using the same logic that Lowell used when postulating Planet X. The problem is that, despite modern technology, it is just so darned far away.
Units for big distances in space were, until recently, based on the distance between Earth and the sun, averaging our furthest and closest orbital distances. This was called an Astronomical Unit (AU) and was used to measure the distances of the other planets in the solar system. The problem is, this metric was not precise enough for measuring really vast distances, like those out to and past Pluto. In 2012, the precise measurement of one AU was set at just under 150 billion meters. The distance to Pluto is about 36.08 (depending on its orbit) AUs away or about 5 million kilometers. Assuming Pluto is at apogee (the furthest part of its orbit), it is just shy of 7.5 trillion meters (with a t) or just over 4 billion miles away. It took the New Horizons spacecraft about nine years to get to Pluto hauling the mail at 58,000 mph. These are truly forbidding distances.
The James Webb space telescope can see about 13.5 billion lightyears into space, which is incredibly far, but it is not the equivalent of taking farseers from the back room and gazing at the moon with them. If there is a dark gas giant in the depths out past the Kuiper belt, there is almost no chance that we could see it. First, the sun’s light would barely illuminate it. We might be able to see it using other spectrums, including infrared (IR) light, depending on what its atmosphere (if any) is composed of but that would mean that we would have to know exactly where to look. At such distances, it is incredibly difficult to precisely localize the sources of the gravitational forces that cause the ETNOs to behave like it’s Old Home Week in the depths of the system. If we cannot see it, it is nearly impossible to know where to look to start the process except where objects are perturbed by odd gravitational disturbances.
The other difficulty is that, unlike mountains or trees or tall buildings, planets move. They orbit the sun at varying speeds so that at any given moment in time there is roughly 360° field where the planet could be. Add to this rather perplexing problem the fact that Earth is also moving and that objects between Earth and the Kuiper Belt could obscure deeper objects, and you get a problem too jangly to consider. Even with the impressive capability of the James Webb Space Telescope.
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If there is a ninth planet roving about in the darkness beyond the Kuiper Belt—incidentally, not a terribly unreasonable theory—it is so far away that we have to sharpen some of our tools to get the data necessary to prove the theory. Of course, nothing depends on whether there is a planet out there or not—well, not really.
Scientists have long assumed that something out there has enough gravity to drag objects passing in the night close enough to make contact with the objects in the Kuiper Belt. Large asteroids are forever being flung out of their own erratic orbits, and getting swatted sunward by a comet or other larger chunk of something. These big space boulders become “planet killers”, hurtling toward the terrestrial planets at fearsome speeds.
If a comet is drawn close to the orbit of an unknown gas or ice giant, possibly larger than Jupiter, and is sent straying into the Kuiper Belt as a result, the chances of it careening into other asteroid-like objects or planetesimals are very high. Frighteningly so. This very scenario may be what caused the Chicxulub asteroid to crater the planet and kill off the dinosaurs. The Trans Neptunian Objects and ETNOs out there in the wastes of our solar system are forever getting lobbed homeward. In June of last year, the asteroid named 2024 MK passed by Earth close enough to make anyone frantic. It missed us by a smaller margin than we would like to consider, given that all the bodies in the local system are moving like proverbial targets at a police urban crime simulation shooting range. Considering the vast distances in space, even just in our local system, for an asteroid to be spotted coming that close to our home ought to wake us to the need to figure out what is going on out there in the borderlands beyond Lowell’s Planet X. If we could get a fix on the possible ninth planet, we might also be able to see big chunks of space rock hurtling at us much sooner.
Until we know for sure, I, like Lowell, will continue to hope there is a dark giant in the deep beyond Pluto, just waiting to be discovered. If so, I hope it happens in my lifetime. I hope they name it Planet X to honor Percival Lowell, who is remembered for his inability to keep his speculations quiet.
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