This Time It’s Aliens: When Interstellar Objects Are Mislabeled as Alien Spacecraft

Image of 3I/ATLAS captured by the Hubble Space Telescope.

A mysterious interstellar object, 3I/ATLAS, is hurtling through our solar system at 58.0 km/s. It’s only the third visitor from outside our solar system we’ve ever detected, an ancient traveler from the Milky Way’s thick disk. Scientific evidence points to 3I/ATLAS being a comet, but mainstream news reporting is dominated by a different question: Could it be aliens?

To cut to the chase, there’s no plausible evidence that 3I/ATLAS is an alien spacecraft, and all the news articles warning of such have the same, rather tenuous, origin. But while this is the latest instance of an interstellar object being mistaken for aliens, it’s not the first. When the first known interstellar traveler, 1I/ʻOumuamua, arrived on the scene in 2017, it was the subject of a similar, but much bigger, alien-related controversy.

The First Visitor

When 1I/ʻOumuamua was discovered in October 2017 from the Pan-STARRS telescope at Haleakalā Observatory, Hawaii, it was the first and only confirmed interstellar object to pass through our solar system. It didn’t take long for speculation to start that the mysterious object was long-awaited evidence of alien intelligence.

The SETI Institute is an organization dedicated to searching for alien life. Naturally, it turned its attention to 1I/ʻOumuamua, observing it on a wide range of radio frequencies just in case it showed signs of extraterrestrial intelligence. This prompted a few speculatory articles that hinted at the prospect of a first contact scenario.¹ With little yet known about the traveler, the possibility that the SETI Institute would detect alien radio signals from it was a tempting subject for reporting. But this was a dead end. After careful radio observation, the SETI Institute found no signs of intelligence, and speculation on 1I/ʻOumuamua’s alien-ness died off for most of a year. Then, in 2018, a single scientific paper kicked alien speculation into high gear.

In October 2018, Harvard professor Avi Loeb and postdoctoral researcher Shmuel Bialy submitted the paper, “Could Solar Radiation Pressure Explain ‘Oumuamua’s Peculiar Acceleration?”² Loeb and Bialy argue that the acceleration shown by 1I/ʻOumuamua is unusual, and propose, as one possible explanation, that the object is really an alien lightsale. A lightsale, or solar sail, is a large, thin surface designed to convert starlight into propulsion. Since it doesn’t need to pack its own fuel, it could theoretically propel itself through space indefinitely, and thereby cross large interstellar distances. But while solar sails are a staple of science fiction, none have yet been identified traveling between the stars. Other scientists disputed Loeb and Bialy’s hypothesis, arguing that the observed acceleration could be caused by comet-like outgassing³ (a process wherein a comet warms as it approaches the sun and releases gases, causing acceleration), and that a solar sail would have to be thinner, and accelerate more noticeably, than 1I/ʻOumuamua.⁴

Nevertheless, Loeb and Bialy’s paper was the spark that lit the fuse on alien speculations. CNN⁵, USA Today⁶, and CBS News⁷ all released articles covering the paper. Despite the fact that the paper itself was highly speculative, that radio observations of 1I/ʻOumuamua turned up nothing unusual, and that the object never did anything that couldn’t be explained by natural phenomena, the speculation on its own was considered newsworthy.

The Current Controversy

In 2025, 3I/ATLAS zoomed into our galaxy at 58.0 km/s, by far the fastest of our known interstellar visitors. In between 1I/ʻOumuamua and 3I/ATLAS, a second visitor, 2I/Borisov, had passed through the solar system. 2I/Borisov escaped suspicion of being an alien intruder, perhaps because it was a very typical comet. The same would not be true of the next visitor.

At first, most news articles focused on how old 3I/ATLAS is. It originates from the Milky Way’s thick disk, which is composed almost exclusively of ancient stars. Estimates of its age range from 3 billion to almost 14 billion years old.⁸ Our solar system is only 4.6 billion years old, so our latest visitor could well be older than it. But as far as news coverage was concerned, it wouldn’t take long for the object’s unusual age to be eclipsed by another line of inquiry.

On July 16, 2025, scarcely more than two weeks after our latest visitor was discovered, Avi Loeb, along with software engineer Adam Hibberd and interstellar propulsion engineer Adam Crowl, published a paper speculating that it was an alien spacecraft.⁹ The paper argued that 3I/ATLAS showed certain anomalous features, such as a lack of cometary outgassing, and therefore might not be a comet at all. Since the object is too small to be an asteroid, the possibility remained that it was an artificially-created extraterrestrial visitor.

The authors of the paper described it as “largely a pedagogical exercise” and predicted, “by far the most likely outcome will be that 3I/ATLAS is a completely natural interstellar object, probably a comet.” Indeed, later evidence has shown that 3I/ATLAS has a solid nucleus surrounded by a cloud¹⁰, and that its composition contains water¹¹, resolving the anomalies referenced in the paper and making its classification as a comet a near certainty.

Most astronomers took “Is the Interstellar Object 3I/ATLAS Alien Technology?” as mere speculation. But the paper had a far-reaching impact on mainstream news reporting. The Independent, which had previously covered 3I/ATLAS in an article¹² that did not speculate that we were heading towards a “first contact” scenario, published a new article¹³ covering the alien hypothesis, and quoting Loeb that “we’d better be ready” for the possibility of benevolent or hostile aliens. Other news outlets covered the paper in still more sensational terms, with headlines such as “Alien attack in November? Harvard scientists warn mysterious object hurtling towards Earth”¹⁴ and “Alien Mothership 3I/ATLAS could reach Earth in just 113 days, says Harvard professor. Will it bring salvation or destruction?”¹⁵ Some conspiratorily-driven news outlets linked the comet’s arrival to the prophecies of Bulgarian mystic Baba Vanga¹⁶ and self-proclaimed inter-dimensional communicator Emily Eaton.¹⁷ US Representative Anna Paulina Luna called Loeb directly for a briefing on 3I/ATLAS, after which she published an open letter urging NASA to use the Juno spacecraft to intercept the object for a closer observation.¹⁸

It’s now just a little over a month since 3I/ATLAS was discovered, and there are already over 100 peer-reviewed scientific papers about it. It seems disproportionate that a handful of speculative papers written by Avi Loeb and his colleagues should dominate media attention. But to many, the mere speculation of incoming alien visitors is either too exciting or too frightening to ignore.

What do we miss when we focus on the possibility of aliens?

There’s nothing wrong with speculating that our latest interstellar visitor could be an alien spaceship, or writing speculative papers to that effect. But we should keep a sense of perspective and not place undue weight on that speculation just because the idea of aliens is exciting. When mainstream news coverage focuses on the most sensational ideas instead of the actual available facts, it deprives the audience of the opportunity to learn those facts, and become invested in the actual scientific discoveries.

1I/ʻOumuamua and 3I/ATLAS are most likely natural objects, but that doesn’t mean they’re boring. 1I/ʻOumuamua’s origins and nature were the subject of scientific debate. Originally classified as an asteroid, later arguments included that it was a comet, a planetary fragment¹⁹, or a a chunk of ice formed in an interstellar cloud.²⁰ Current evidence suggests it was a comet.²¹ 3I/ATLAS, meanwhile, is an ongoing subject of observation. As an object potentially older than our solar system itself, it may have interesting secrets to reveal. By March of 2026, this latest visitor will be heading past Jupiter on its way out of our solar system. Whether it’s remembered for its interesting qualities, its unusual age and speed, or only as a source of alien-related controversy, is up to us.

With our limited sky-surveying capabilities, we’ve only been able to catch three interstellar visitors so far. But an estimated three such objects enter our solar system every day.²² With more sophisticated sky surveys planned for the near future²³ the number we can detect will likely rise dramatically in the coming years. We may have the opportunity to study other objects as ancient as 3I/ATLAS, or whose compositions prove to be interesting puzzles like 1I/ʻOumuamua. We may see objects that raise interesting questions, and help us unravel mysteries of the universe. I hope that people won’t move on and lose interest when they realize that aliens probably aren’t going to show up on our doorstep.

Category: Astronomy

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Clio Heard