Astronomers are tracking 3I/ATLAS, only the third known interstellar object to pass through our solar system. It’s likely a comet; the closest it will get to Earth is about 170 million miles, and it should come within ~130 million miles of the Sun on October 30 before fading from view until around December.

As it approaches the Sun, 3I/ATLAS is getting more active. On August 27, Gemini South images showed a much longer tail, consistent with ice and dust heating up and venting—behavior similar to comets formed within our own system.

Harvard astronomer Avi Loeb, who has floated (but not insisted on) an alien–technology angle for such objects, now notes a strange “anti-tail” pointing toward the Sun rather than away from it. He argues this isn’t a perspective effect and says such a feature hasn’t been reported for solar-system comets.

While most observations fit a natural comet, the unusual anti-tail—and differences from prior interstellar visitors—make 3I/ATLAS a rare and intriguing target as scientists race to study it before it slips back into the dark.