In July 2025, scientists noticed something rare. An interstellar object tore through our solar system at 137,000 mph. Rumors followed. Some scientists theorized it could be a probe sent by an alien civilization to study our neighborhood.

Professor Avi Loeb of Harvard cited three reasons 3I/ATLAS might be an alien spacecraft. First, its trajectory is highly unusual. The object passed through space relatively close to multiple planets while the sun shielded it from Earth-based observation.

Second, it initially lacked a traditional comet tail. That detail led some to speculate its surface might be metallic. The object has since begun standard cometary outgassing.

Finally, its sheer size raised eyebrows. 3I/ATLAS measures roughly the size of Manhattan.

Many scientists remained skeptical. That skepticism comes with the job. Still, researchers studying interstellar objects were eager for a closer look.

Benjamin Jacobson-Bell of the University of California, Berkeley, said, “There is considerable excitement around 3I/ATLAS because it’s only the third-ever discovery of an interstellar object within our solar system,” he continued. “Sending spacecraft to other star systems could be very informative, so it’s tempting to imagine that some interstellar objects might be intentional probes.”

Jacobson-Bell and his colleagues work on the Breakthrough Listen project, which searches for alien technosignatures. As 3I/ATLAS passed closest to Earth, the team focused its attention on the object. “If we don’t look, we’ll never know.”

How scientists searched for signs of alien technology

The researchers had the perfect tool for the job.

“The Green Bank Telescope is a radio dish 100 meters wide, situated in a zone federally regulated to be free of most radio interference.” Translation: The scientists had the best chance on Earth to detect any technology aboard the object. “If there were any transmitters on 3I/ATLAS up to ten times weaker than a cell phone, we would have found them.”

The team concluded that 3I/ATLAS is a natural interstellar object. It is a comet. Jacobson-Bell acknowledged a few false alarms during the observations. The team later traced those signals back to Earth-based radio interference.

For conspiracy theorists still championing Loeb’s idea, scientists share the enthusiasm. Discovering an alien probe would define a career. “We all would have been thrilled to find technosignatures”

Jacobson-Bell welcomes the attention surrounding 3I/ATLAS. “We hope that public interest in interstellar objects remains strong — they’re very interesting whether they’re spacecraft or comets, and it’s entirely possible that one day, one of them will indeed be transmitting technological signals.”