As the winter solstice approached, the night sky held a secret far more intriguing than any festive light display. While most of Britain was hunkered down for the December chill, a silent, interstellar trespasser was making its closest pass to Earth. 3I/ATLAS—officially designated C/2025 N1—was discovered on 1 July 2025 by astronomer Larry Denneau using the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) in Río Hurtado, Chile. The third confirmed visitor from the depths of interstellar space, it has spent the tail end of 2025 challenging everything astronomers thought they knew about wandering cosmic bodies.
Fresh research has now pulled back the curtain on this visitor's most bizarre feature: a 'sun-facing' tail that appears to be throwing a cosmic tantrum. While typical comets sport tails that stream away from the Sun like windblown hair, 3I/ATLAS boasts a rare 'anti-tail' that points directly at our star. Even more baffling, this structure—stretching an incredible 620,000 miles (one million kilometres) into the void—was observed 'wobbling' with mechanical precision every 7 hours and 45 minutes as it made its approach.
