For nearly a decade, astronomers have been searching for a hypothetical giant planet that may lurk in the distant reaches of the solar system. 

We could be on the brink of discovering this new world, known as Planet Nine, assuming it exists. Later this year, the Large Synoptic Survey Telescope (LLST) at the Vera C. Rubin Observatory in Chile will open its eyes to the sky for the first time. Planet Nine, if it’s out there, is very likely to pass through its sights.

The discovery of a new planet in the solar system would be a scientific goldmine and a satisfying resolution to a long-standing mystery. It would also be a major public sensation that could inspire wonder, controversy, and a whole lot of unhinged speculation. It’s dizzying to imagine how such an event might be culturally metabolized at this point of the 21st century, during a renaissance of infotainment, conspiracy theories, and ascendent popular dreams of human space colonization. 

To make predictions, it might be helpful to look to the past. The public reactions to the discoveries of Uranus, Neptune, and Pluto — as well as the brouhaha sparked by Pluto’s subsequent demotion to a dwarf planet — can help set some expectations for the dramatic entrance of a new member of the solar family.

“I think it will be a moment where people are genuinely excited about something new in space,” said Mike Brown, an astronomer at Caltech who co-developed the Planet Nine hypothesis, in a call with Supercluster. “People love space. People love the solar system. The solar system is, in many ways, the largest neighborhood that anybody knows about.” 

Brown and his colleague Konstantin Batygin, also an astronomer at Caltech, first proposed the Planet Nine hypothesis in 2016 to explain strange phenomena in the outer solar system. The team observed that some Trans-Neptunian objects (TNOs), a class of minor planets beyond the orbit of Neptune, had oddly clustered orbits that hinted at the presence of a massive object even further out in the solar wilderness.   

“The 2016 study was very preliminary,” Brown said. “We had only a limited set of observations and computer simulations to try to understand where it might be. We've narrowed it down now, and have a pretty good predicted swath across the sky of where it's supposed to be, if our assumptions are correct.”

The spectre of a ninth planet has inspired intense media coverage as well as spirited scientific debate. Some researchers have cast doubt on the hypothesis, and presented alternate explanations for the TNO observations, such as the presence of a massive ice disk or modified theories of gravity. Other teams have built on the hypothesis and proposed constraints on the possible properties of the planet. Current estimates place Planet Nine anywhere from 400 to 800 times as far from the Sun as Earth, and suggest that it is about 4 to 10 times as massive as Earth. 

LSST, which will scan expansive swaths of the sky with unprecedented precision, may swiftly resolve the matter. The survey will continuously release its observations for anyone to access, which means skywatchers of all stripes will be racing to spot the first glimpse of Planet Nine.

“If LSST does detect a new planet, it will most likely be through a community effort, with various groups of astrophysicists running their own algorithms on LSST’s nightly stream of 10 million transient alerts, which are records of changes in the night sky,” Amir Siraj, an astrophysicist at Princeton University who led a recent study about Planet Nine’s properties, told Supercluster in an email. “These algorithms would search for a faint speck of reflected sunlight moving extremely slowly across the sky.”

This is not remotely the first time that astronomers have searched for a hypothetical planet by following orbital breadcrumbs. In 1800, a group that became known as the Celestial Police began chasing the ghost of a hidden planet between Mars and Jupiter, which eventually led to the discovery of the asteroid belt. 

On September 23, 1846, Neptune was officially discovered with calculations made by the French mathematician Urbain Le Verrier, but it was such a close finish that the British astronomer John Couch Adams campaigned for mutual credit. The ensuing dispute over who should lay claim to the discovery enraptured the public and became a matter of national pride.  

“The history since the discovery of the planet is, I think, more curious than that before the discovery,” commented the astronomer Sir George Biddell Airy in 1847.

Given the similarly competitive spirit of the hunt for Planet Nine, any news about a detection would likely make it out to the public quickly, no doubt sparking a media frenzy.

“It's going to be a free-for-all,” Brown said. ”If we find it, we will announce it within days because the data are all out there. People will want to start studying it.”  

Siraj predicted that details about the planet’s discovery would rapidly be published on arXiv, a server for preprint studies, setting off a cascade of news coverage and follow-up observations.

“Almost every large telescope — both ground-based and space-based — would then be directed toward that patch of sky using ‘target of opportunity’ or ‘discretionary time’ procedures,” he said, noting that heavyweight observatories, including JWST and Hubble, would likely be enlisted to confirm or refute the findings.  

Given that many people will be rushing to spot Planet Nine, another Neptune-style spat over credit may erupt in the aftermath of a discovery. This scenario would make for great news content, as the identity of a planet’s discoverer is often more meaningful than the actual planet in the eyes of onlookers. 

For instance, take this 1932 report documenting local backlash in the hometown of Clyde Tombaugh, Pluto’s discoverer, after he was overlooked in a popular astronomy handbook.

“The wheat farmers and livestock railers [of Burdett, Kansas] profess little knowledge of astronomy, but they are loyal to Clyde Tombaugh, the farm boy who discovered the planet Pluto,” according to the article, which goes on to describe the community’s “ire” and “resentment over the slight” of Tombaugh’s exclusion from what they see as his rightful place in history.

In other words, the “who” in a planetary discovery is at least as important as the “what” in many cases. The personal element may be even more important with Planet Nine because, in addition to making history, the team that spots it will likely receive the combustible honor of naming a whole new world.

At a time when the established names of locations on Earth are being litigated, it’s easy to imagine heated clashes over what name to bestow on an entirely new planet of the solar system.  

“Naming rights would go to the discoverers, and whatever the discoverers choose is likely to stick,” Siraj said, adding that “it will surely provoke major arguments and differences of opinion no matter what name is chosen.”

There is, again, historical precedent for this issue. For instance, it took the international astronomical community nearly 70 years to agree on the name Uranus for the seventh planet. William Herschel, who discovered Uranus in 1781, initially proposed the name Georgium Sidus (George’s Star) after his patron King George III. Unsurprisingly, this name didn’t catch on with astronomers in other countries, leading to a parade of alternate names including Hypercronius, Transaturnis, Minerva, Herschel, and the eventual survivor: Uranus.  

Le Verrier, who discovered Neptune, exercised his naming rights by choosing its present name, after the Roman god of the sea, though he changed his mind later and unsuccessfully tried to name it after himself. Pluto was named within months of its discovery by Tombaugh; the name was chosen in part to honor Percival Lowell (initials P.L.) who spent the final years of his life consumed with the unrealized dream of finding a “Planet X” that turned out to be Pluto. 

“We felt in making our choice of a name for Planet X that the line of Roman gods for whom the other planets are named should not be broken,” said Roger Lowell Putnam, Lowell’s nephew and trustee, in a New York Times article published on May 25, 1930 (Pluto was discovered on February 18 of the same year). “We believe that Dr. Lowell, whose researches led directly to its discovery, would have felt the same way.”

But though Uranus, Neptune, and Pluto are all namesakes of Roman gods, we've now almost exhausted this pantheon on existing celestial objects, including minor planets like Vesta, Ceres, and Eris. It may be that Planet Nine bucks the mold with a very different kind of moniker.

“The discoverer has the right to officially propose a name to the International Astronomical Union, and they will accept it unless there’s some reason not to,” Brown said. 

For instance, if the discoverers propose a dumb or controversial name, like McPlanetface or Catturd-3, the IAU could push back on the choice. Otherwise, the name presented by the discoverers will be formalized.

Brown is well-acquainted with culture wars fueled by strong sentiments about planet nomenclature and categorization. He led the effort to reclass Pluto as a dwarf planet in 2006, a move that was viewed by many Pluto enthusiasts as a wanton insult against their favorite world. Brown has taken the whole episode in stride, referring to himself as the “Pluto killer.” 

“I was surprised, honestly, that astronomers ever had the guts to vote to demote Pluto,” he said. “I'm glad the vote was the way it was, because that was absolutely the correct thing to do. But it took a lot of guts to do that against what was going to be a certain backlash.”

Famous as the Pluto killer, Brown now looks forward to an opportunity to replace the beloved dwarf world with a real, bonafide ninth planet.

If Planet Nine exists, “it is the fifth largest planet of our solar system,” Brown said. “This is a monster out there.” 

“Showing what a real new planet looks like puts to bed the question of why we don't call Pluto the ninth planet,” he added. “This is what a real planet looks like.”

Space means very different things to different people. It can be the arena of scientific research. It can be a spiritual tapestry. It can be a staging ground for conspiracy theories, populated by UFOs, apocalyptic omens, and the ruins of alien civilizations. 

Meanwhile, as Elon Musk becomes more politically and culturally relevant, so too does his vision of space as a salvatory frontier that must be colonized to secure humanity’s future. Throwing a new planet into this swirling semantic maelstrom is sure to provoke a wide range of reactions.

“What you have got to be prepared for, with anything these days, is simply whether or not establishment science will be trusted,” said Ian Reyes, a professor of communication and media at the University of Rhode Island who has previously studied space-related conspiracy theories, in a call with Supercluster. 

“Absolutely any conclusion, because of where it comes from, is prone to be questioned,” he continued. “Oh, there's another planet. Why? Is Elon Musk going to build a mansion there? Did he put it there? Why wasn't this planet there before? Am I still a Gemini if there's a new planet?”

These ruminations are, often, extremely fun. In fact, their spellbinding appeal can put scientists and science communicators in a familiar bind: The more that scientists assert a status as gatekeepers of astronomical knowledge, the more tinder is available to ignite the infotainment and conspiracy spheres.   

“Establishment science is absolutely needed for certain forms of evidence to get a conspiracy theory going,” Reyes said. “It’s super-respected in some cases, but there's that moment where you get a rhetorical turn, where now we can't trust the science for some reason. That's where you open up that space for play.”

“When you compare the lack of science literacy in the public to the incredible conspiracist literacy people have, you realize that science is competing with an infotainment industry that gets people at a rather young age,” he added.

In other words, we can expect the reappearance of perennial theories about fictional worlds like Nibiru, alongside a blossoming of creative new plotlines, adapted to the current zeitgeist.

“I guarantee you that as soon as it's discovered and the first person sees a plot of its orbit, there will be YouTube videos about Nibiru and how it's going to come in and destroy the Earth,” Brown said. “Absolutely, it's going to happen. It already has. I have discovered Nibiru at least three separate times in my career, apparently. Every time I find something with an eccentric orbit and announce it, it gets a YouTube video about how it's going to destroy the Earth.”

Or, possibly, the whole thing could fizzle into a proverbial nothingburger. In fact, this would be the one scenario that might truly depart from the example of past planetary histories. The discoveries of Uranus, Neptune, and Pluto were welcomed by the public, and the scientists who spotted them became international celebrities. But perhaps, in the claustrophobic media environment we now inhabit, the novelty of a new planet will turn out to be a lack of novelty.

“What would be extraordinary, super-special, or ‘once-in-a-lifetime’ to a researcher, might just be a cool Monday morning news item to somebody, especially in the present flood of information,” Reyes said.

Like so much about life on Earth, the view will depend on where people are standing and what they stand for. But regardless of the myriad outcomes, Planet Nine, if discovered, will push the boundaries of the solar system out to a new horizon, both literally and in the public consciousness.

“The planets are one of the first things we learn about in school, forming a fundamental part of how we as humans understand our place in the universe,” said Siraj. “Adding a new member to this familiar list — especially 180 years after the last major addition (Neptune) — would feel like a profound shift in our knowledge of our cosmic context.” 

“After all, the solar system is our home in the universe,” he concluded. “Look no further than the discovery and then subsequent recategorization of Pluto for a reminder of how much we care, as residents of the third planet from the Sun, about planetary membership of our solar system.”