Comet or Alien Probe? Harvard’s Avi Loeb Revives Debate Over Mysterious Interstellar Visitor 3I/ATLAS

In a story that seems torn from the pages of science fiction, a newly discovered interstellar object—3I/ATLAS—has reignited one of the most controversial conversations in modern astronomy: Could it be alien technology?

Originally confirmed by NASA in July, 3I/ATLAS is only the third known object to ever pass through our solar system from beyond, following the path carved by 1I/ʻOumuamua and 2I/Borisov. Estimated to be more than 12 miles wide and traveling at a breakneck 37 miles per second, this cosmic visitor will come within 130 million miles of Earth on October 30. By all conventional accounts, it looks, acts, and behaves like a typical interstellar comet—icy, fast, and uninterested in anything but cruising past the sun.

But one group of scientists isn’t quite ready to close the case.

At the center of the debate is Dr. Avi Loeb, a prominent yet often polarizing astrophysicist from Harvard University, known for his bold theories about intelligent extraterrestrial life. Loeb and his co-authors have published a new paper that challenges the conventional view of 3I/ATLAS as just another space rock. Instead, they dare to ask: What if it’s a piece of alien technology?

The idea isn’t new for Loeb. In 2018, he made headlines around the world for suggesting that 1I/ʻOumuamua—another strange, fast-moving interstellar object—might have been an alien probe. His critics argue that such claims are sensational and speculative. Loeb argues that scientific progress demands asking uncomfortable questions, especially when faced with anomalies that don’t fit neatly into existing models.

While Loeb and his team openly acknowledge that they don’t have definitive proof—nor are they declaring with certainty that 3I/ATLAS is an alien spacecraft—they emphasize the importance of keeping our minds open in the face of cosmic mysteries. “Extraordinary claims require extraordinary evidence,” Loeb has said in the past, “but dismissing possibilities without investigation is unscientific.”

So far, the scientific consensus still leans toward 3I/ATLAS being a comet. It exhibits the classic behavior: outgassing as it nears the sun, moving on a hyperbolic trajectory that suggests it originated far beyond our solar system.

Still, Loeb's hypothesis has found both fascinated supporters and harsh skeptics. Some argue it's a much-needed challenge to scientific complacency. Others see it as a distraction from more plausible research.

Regardless of which side you're on, one thing is clear: 3I/ATLAS is stirring up big questions about our place in the universe—and whether we might not be as alone as we think.

As it speeds past Earth this fall, scientists will be watching closely. Whether it's a chunk of ice, a space rock with a story, or—just maybe—an alien artifact, 3I/ATLAS is a reminder of how little we truly know about the vastness beyond our skies.