The Endless Wonder and Beautiful Uncertainty of Interstellar Comets

On December 19, 2025, 3I/ATLAS—a comet from another solar system—quietly made its closest pass to Earth at a distance of 270 million kilometres, nearly twice as far away as the sun. It was my son’s birthday. I thought about the interstellar visitor as my daughter, wife, and I took turns dragging his wandering monster truck balloon back to the table and again, later that day, as he exhaled a wish through the golden candle on his birthday brownie.

For months, speculation had swirled about this strange comet, with its peculiar features and behaviour, including the fact that its tail pointed toward the sun rather than away from it. Where did it come from? How old was it? Terrestrial and space-based telescopes had trained their lenses on the object, with its nucleus estimated by the National Aeronautics and Space Administration’s Hubble Space Telescope to be between 440 metres and 5.6 kilometres wide, big enough to swallow the entirety of Toronto’s downtown. NASA, the European Space Agency, and the China National Space Administration reprogrammed spacecraft en route to Jupiter and orbiting Mars to snap pixelated photos of 3I/ATLAS. As the comet drifted the closest it would ever be to this insignificant blue dot we call home, I found myself wondering: Was 3I/ATLAS thinking about us?

Since it was first clocked on July 1, 3I/ATLAS—named for the Asteroid Terrestrial-impact Last Alert System (ATLAS), a NASA-funded telescope network developed and operated by the University of Hawaii and NASA—had occupied an outsized place in the public imagination, including sincere discussion that it could be alien technology. Maybe people were looking for a distraction from the geopolitical tension dominating the daily news. Or maybe the rise and increasing sophistication of TikTok and YouTube algorithms had amplified the discourse. The United States government funding crisis didn’t help. NASA’s temporary shutdown between October and November created a brief information vacuum that fuelled a conspiracy narrative. Celebrities spread the word. Kim Kardashian tweeted at NASA, asking for clarity about 3I/ATLAS, and Elon Musk mused about the comet on The Joe Rogan Experience, while the comment threads, TikTok explainers, and speculative headlines turned this distant space object into a cultural event.

It wasn’t the first time an interstellar comet sparked a tug-of-war between the limits of scientific reasoning and a culture seemingly desperate for cosmic meaning.

In October 2017, Robert Weryk was sitting in a hotel room in Utah during the American Astronomical Society’s Division for Planetary Science conference, parsing through asteroid data, when he came across an object with an unexpected orbit. Weryk is a Canadian astronomer with Western University who works with the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS). Based in Hawaii, the system tracks comets and asteroids whose orbits bring them close enough to Earth’s orbit to pose a threat and require monitoring. NASA’s Near-Earth Object database currently lists around 2,532 potentially hazardous asteroids—Pan-STARRS has played a significant role in many of these discoveries. Part of Weryk’s research is to review nightly asteroid detections.

On that evening in Utah, Weryk sent an email to his adviser and another colleague telling them the asteroid’s position didn’t make sense. They started comparing the object’s trajectory across three nights. “If you see something unexpected like this, you want to be absolutely sure,” he tells me. “You go back and recheck your measurements.”

Weryk’s colleague gathered his own data and confirmed: the orbit was interstellar. “We’re like whoa . . .” he says. “No one’s ever seen one of these before.” They collected a fourth night’s data from a separate telescope, the Canada–France–Hawaii telescope. “It sealed the deal,” says Weryk. “We knew instantly that we had something very special.”

For hundreds of millions of years, this strange, elongated, seemingly starship-shaped space rock, ten times longer than it is wide, has wandered the Milky Way through star systems, nudged by gravity, shaped by cold, alone and untethered, before being caught by the lens of our terrestrial paparazzi. With help from a Hawaiian linguistics team, the object was named 1I/‘Oumuamua, which Weryk says translates to a messenger from afar arriving first. “Scientifically,” he says, “it is reaching out and giving us something.”

The peculiarity of ‘Oumuamua’s shape was enough to prompt scientists on the Breakthrough Listen project—an initiative funded by Russian-born Israeli tech investor and billionaire Yuri Milner and his wife, Julia, to search for signs of extraterrestrial technology—to sweep the object for radio signals in December 2017. Their search didn’t turn up any definitive evidence, and ‘Oumuamua remained a remarkable—but natural—celestial object.

A year later, Avi Loeb, an astrophysicist, published a paper on “‘Oumuamua’s peculiar acceleration.” (Loeb is head of Harvard University’s Galileo Project, an initiative focused on researching interstellar objects and Unidentified Aerial Phenomena, or UAPs—formerly UFOs.) “One possibility is that ‘Oumuamua is a lightsail, floating in interstellar space as a debris from an advanced technological equipment,” Loeb and co-author, Shmuel Bialy, proposed. Soon, news outlets, including ABC, Time, and Space.com were reporting on the alien technology interpretation.

Then we found another visitor.

On August 30, 2019, Crimean amateur astronomer Gennady Borisov spotted an interstellar object as it ripped through our solar system at 177,000 kilometres per hour. Scientists identified the object as a comet and named it 2I/Borisov, after its spotter. While there was virtually no mainstream speculation Borisov was anything other than a comet, it told us something else: these interstellar visitors may be more common than we thought. The first two occurred within twenty-two months, says Weryk. “These were probably happening before; it’s just nobody ever saw them.”

Or maybe they got lost. Survey telescopes pan across the night sky, capturing several images of an area before moving on to the next one. Software combs the findings, looks for moving stars and tags them. Astronomers then go back to try to get telescopic images of these moving objects. “This confirms that the object is real and what its initial orbit is,” Weryk says. But sometimes the object is not where it’s predicted to be, or the weather is bad and the telescope isn’t operating. “We actually would’ve discovered the second interstellar object, Borisov,” says Weryk. “But the month we would’ve found it, there was an ice storm on Maui, and our telescope was closed.”

Weryk estimates he and his colleagues have lost over a thousand asteroids to positional uncertainty. There’s too much nothingness up there. Even with the sharpest of calculations, the vastness wins. “It’s entirely possible that at least one of these thousand was an interstellar object that we just couldn’t find again,” he says.

But the interstellar objects we have managed to find have triggered fascinating discourse. Especially 3I/ATLAS. I loved reading the dense and near daily debriefs of Loeb, who took to Medium on July 16 to announce a paper he had written with colleagues, “Is the Interstellar Object 3I/ATLAS Alien Technology?” Even as NASA, freshly operational after the shutdown, announced on November 19 that 3I/ATLAS was, conclusively, a natural comet, not technology, Loeb continued tracking the comet and publishing his analysis on Medium, challenging the official narrative, asking what if?

By January 15, he’d identified seventeen anomalous behaviours, including the unusually high presence of nickel in the comet’s gas plume, which he said could indicate a technological origin and a trajectory that brought it close to Jupiter and Mars but limited detailed observation from Earth. Loeb questioned whether this could be perceived as intentionality. Was the comet avoiding our telescopes at its closest pass?

I was curious about Loeb’s feelings on the reaction to his work—the magnetism of his alien technology theory, the pushback from the astronomy community—so I reached out. He expressed distaste for the clickbait-y nature of how his research is portrayed in the media. “People report things that I don’t say,” he says. “Then scientists respond to what the reporter said as if it’s what I said, which is really unfortunate.”

Science, says Loeb, operates similarly to religion: everyone agrees to some fundamental truth and puts it on a pedestal. In other words, scientifically, we can’t talk about aliens or alien technology. It’s too low brow, too taboo. “Suppose you always say everything in the sky is a rock, and you are never willing to consider the possibility publicly that it might be something else—then you will never find it,” says Loeb. “It’s a self-fulfilling prophecy.”

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I ask Jon Willis, an astronomer at the University of Victoria and author of The Pale Blue Data Point: An Earth-Based Perspective on the Search for Alien Life, about the alien speculation surrounding these interstellar visitors. He reminds me that, in the 1890s, American businessman Percival Lowell helped fuel early speculation about canals on Mars and intelligent life beyond Earth. “He didn’t make up his observations; they were real,” says Willis.

Lowell’s telescope was too low resolution to accurately identify what he was seeing on the Martian surface. “He basically saw an optical illusion and wanted to run with it,” says Willis.

Willis argues that the real wonder is that interstellar visitors, once thought fantastically rare, are beginning to look like regular travellers through the solar system. As detection improves, he suggests, it’s completely plausible that we will find a way to take samples from these visitors—much like how the Japan Aerospace Exploration Agency’s Hayabusa2 mission, in 2014, and NASA’s OSIRIS-REx mission, in 2023, gathered samples from asteroids.

To collect a piece of an interstellar comet would be to hold the material memory of some distant solar system’s beginning in our hands. “We’ve dreamed in science fiction of going to the stars and studying them with futuristic space missions,” says Willis. “But isn’t it amazing that, within our lifetime, we could?”

Loeb shares Willis’s interest in what a few grams of an interstellar comet could tell us about places we could never reach in the entirety of human civilization’s lifespan. But there is also a possibility that we will find an object like the Voyager spacecraft, he says, referring to the pair of probes we launched in 1977 with gold-plated copper phonograph records containing greetings, etchings, images, and even the sound of a human heartbeat.

The gold records, designed to last a billion years and represent Earth’s diversity to any extraterrestrial life that might stumble upon them, are still out there travelling through the Milky Way—on a different interstellar trajectory than 3I/ATLAS. “If another civilization finds Voyager after it exits the solar system, then they would consider it an interstellar object,” says Loeb. What if 3I/ATLAS is something or someone else’s Voyager?

A few weeks before 3I/ATLAS made its closest pass to Earth, my seven-year-old daughter called me out onto the porch to look at a string of lights in the star-filled sky. I later learned it’s a Starlink Train, a series of satellites launched by SpaceX the previous night. But for a moment, my brain—drunk on 3I/ATLAS debriefs and the cosmic hope we were living in a moment of unprecedented discovery that tells us we’re not alone—couldn’t compute. I knew there was an explanation. I believed there was.

In the moments after seeing the lights, I called my neighbours over to have them stare at the same star-filled sky and tell me they too saw this strange, impossibly long line of lights passing by. I told myself that was enough, that if we could all see it together, the world would be knowable again. In the end, it wasn’t the wonder or hope that won out; I needed the security in knowing it was human-made, the security of the scientifically backed status quo.

In the darkness, I heard my daughter say to my neighbour that she’d been waiting her whole life to see something like this, and I realized, to her, it wasn’t something to be understood; it didn’t need a tidy answer. Just seeing it was enough.